[IMP] web: add buttons in control panel without selection in list

This commit adds the possibility to define buttons that are always
present in the arch of a list view.

Purpose:
Several customisations of the list view consist in adding an always
present button in the control panel that performs an action/calls a
model's method.
We want to support this feature directly in the framework to remove
these customisations.

Solution:
Add a "display" option that lets you know when to display a button.
The different values that can be assigned to "display":
- "selection": the button is only displayed if at least one record is selected.
- "always": the button is always displayed.
The default value of "display" is "selection".

Exemple:
<tree>
    <header>
        <button name="to_do" type="object" string="Do" display="always"/>
    </header>
</tree>

Taskid: 3082303
Part-of: odoo/odoo#106519

addons/web/static/src/views/list/list_controller.xml

@@ -47,26 +47,26 @@
                         Create
                     </button>
                 </t>
-                <t t-if="nbTotal and !nbSelected and activeActions.exportXlsx and isExportEnable and !env.isSmall">
-                    <button type="button" class="btn btn-secondary fa fa-download o_list_export_xlsx" data-tooltip="Export All" aria-label="Export All" t-on-click="onDirectExportData"/>
-                </t>
-            </t>
-            <t t-if="nbSelected">
                 <t t-foreach="archInfo.headerButtons" t-as="button" t-key="button.id">
                     <ListViewHeaderButton
+                        t-if="nbSelected || (button.display === 'always')"
                         list="model.root"
+                        className="button.className"
                         clickParams="button.clickParams"
-                        defaultRank="button.defaultRank"
+                        defaultRank="'btn-secondary'"
                         domain="props.domain"
                         icon="button.icon"
                         string="button.string"
                         title="button.title"
                     />
                 </t>
-                <t t-if="!env.isSmall">
-                    <t t-call="web.ListView.Selection"/>
+                <t t-if="nbTotal and !nbSelected and activeActions.exportXlsx and isExportEnable and !env.isSmall">
+                    <button type="button" class="btn btn-secondary fa fa-download o_list_export_xlsx" data-tooltip="Export All" aria-label="Export All" t-on-click="onDirectExportData"/>
                 </t>
             </t>
+            <t t-if="!env.isSmall and nbSelected">
+                <t t-call="web.ListView.Selection"/>
+            </t>
         </div>
     </t>
 

addons/web/static/src/views/utils.js

@@ -208,6 +208,7 @@ export function processButton(node) {
         string: node.getAttribute("string") || undefined,
         options: JSON.parse(node.getAttribute("options") || "{}"),
         modifiers: JSON.parse(node.getAttribute("modifiers") || "{}"),
+        display: node.getAttribute("display") || "selection",
         clickParams: {
             close: archParseBoolean(node.getAttribute("close"), false),
             context: node.getAttribute("context") || "{}",

addons/web/static/tests/views/list_view_tests.js

@@ -810,7 +810,7 @@ QUnit.module("Views", (hooks) => {
         );
         cpButtons = getButtons(target);
         assert.containsOnce(cpButtons[0], 'button[name="x"]');
-        assert.hasClass(cpButtons[0].querySelector('button[name="x"]'), "btn btn-secondary");
+        assert.hasClass(cpButtons[0].querySelector('button[name="x"]'), "btn btn-secondary plaf");
         assert.containsOnce(cpButtons[0], ".o_list_selection_box");
         assert.strictEqual(
             cpButtons[0].querySelector('button[name="x"]').nextElementSibling,
@@ -827,6 +827,54 @@ QUnit.module("Views", (hooks) => {
         assert.containsNone(cpButtons[0], 'button[name="y"]');
     });
 
+    QUnit.test(
+        "list view: action button in controlPanel with display='always'",
+        async function (assert) {
+            await makeView({
+                type: "list",
+                resModel: "foo",
+                serverData,
+                arch: `
+                <tree>
+                    <header>
+                        <button name="display" type="object" class="display" string="display" display="always"/>
+                        <button name="default-selection" type="object" class="default-selection" string="default-selection"/>
+                    </header>
+                    <field name="foo" />
+                </tree>`,
+            });
+            let cpButtons = getButtons(target)[0];
+            assert.deepEqual(
+                [...cpButtons.querySelectorAll("button")].map((button) =>
+                    button.textContent.trim()
+                ),
+                ["Create", "display", ""]
+            );
+
+            await click(
+                target.querySelector('.o_data_row .o_list_record_selector input[type="checkbox"]')
+            );
+            cpButtons = getButtons(target)[0];
+            assert.deepEqual(
+                [...cpButtons.querySelectorAll("button")].map((button) =>
+                    button.textContent.trim()
+                ),
+                ["Create", "display", "default-selection"]
+            );
+
+            await click(
+                target.querySelector('.o_data_row .o_list_record_selector input[type="checkbox"]')
+            );
+            cpButtons = getButtons(target)[0];
+            assert.deepEqual(
+                [...cpButtons.querySelectorAll("button")].map((button) =>
+                    button.textContent.trim()
+                ),
+                ["Create", "display", ""]
+            );
+        }
+    );
+
     QUnit.test(
         "list view: action button executes action on click: buttons are disabled and re-enabled",
         async function (assert) {

odoo/addons/base/rng/common.rng

@@ -360,6 +360,7 @@
             <rng:optional><rng:attribute name="title"/></rng:optional>
             <rng:optional><rng:attribute name="aria-label"/></rng:optional>
             <rng:optional><rng:attribute name="aria-pressed"/></rng:optional>
+            <rng:optional><rng:attribute name="display"/></rng:optional>
             <rng:zeroOrMore>
                 <rng:choice>
                     <rng:ref name="field" />