[IMP] base, mail: split company email colors from document colors

PURPOSE

Settings allow to change colors used in emails (primary and secondary colors).
Those are used for headers and buttons. They are currently shared with colors
used for base documents and reports layout: changing email colors change
documents colors, which is not expected nor clearly indicated.

SPECIFICATIONS

Split configuration: colors used in documents may differ from colors used in
emails. Duplicate color fields (primary and secondary). To ease setup when
updating documents colors, update mail colors accordingly. Inverse is not
true as we consider documents being the main configuration, and emails a
more fine-grain configuration.

Task-3346388

Part-of: odoo/odoo#123678

addons/digest/data/digest_data.xml

@@ -11,7 +11,7 @@
         <meta name="viewport" content="width=device-width; initial-scale=1.0; maximum-scale=1.0; user-scalable=no;"/>
         <meta http-equiv="X-UA-Compatible" content="IE=9; IE=8; IE=7; IE=EDGE" />
         <style type="text/css">
-            <t t-set="color_company" t-value="company.secondary_color or '#875a7b'"/>
+            <t t-set="color_company" t-value="company.email_secondary_color or '#875a7b'"/>
             /* Remove space around the email design. */
             html,
             body {
@@ -360,7 +360,7 @@
                                                             <t t-set="kpi_subtitle" t-value="kpi_info['kpi_col1']['col_subtitle']" />
                                                         </div>
                                                     </td>
-                                                    <td t-if="kpi_info.get('kpi_col2')" class="kpi_cell" t-att-style="'border-top: 2px solid ' + (company.secondary_color or  '#875a7b')">
+                                                    <td t-if="kpi_info.get('kpi_col2')" class="kpi_cell" t-att-style="'border-top: 2px solid ' + (company.email_secondary_color or '#875a7b')">
                                                         <div t-call="digest.digest_tool_kpi">
                                                             <t t-set="kpi_value" t-value="kpi_info['kpi_col2']['value']" />
                                                             <t t-set="kpi_margin" t-value="kpi_info['kpi_col2'].get('margin')" />