[FIX] web: fixed width for icons in view_button

Since the introduction of Milk design[1], the fixed width for icons has
been removed in `view_button`.
This creates alignment issues when we have several buttons with icons
displayed in a grid or list (eg. status buttons).

This commit fixes this issue.

[1] commit 824024f

task-3387198
Part of task-3326263

closes odoo/odoo#127090

X-original-commit: a801dc6c74031e5593063ccac0245b2fe32c8ef3
Signed-off-by: Pierre Paridans (app) <app@odoo.com>

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

@@ -25,10 +25,10 @@ function iconFromString(iconString) {
     const icon = {};
     if (iconString.startsWith("fa-")) {
         icon.tag = "i";
-        icon.class = `o_button_icon fa ${iconString}`;
+        icon.class = `o_button_icon fa fa-fw ${iconString}`;
     } else if (iconString.startsWith("oi-")) {
         icon.tag = "i";
-        icon.class = `o_button_icon oi ${iconString}`;
+        icon.class = `o_button_icon oi oi-fw ${iconString}`;
     } else {
         icon.tag = "img";
         icon.src = iconString;