feature #48343 [Form] [ChoiceType] Add a placeholder_attr option (elementaire)

This PR was merged into the 6.3 branch.

Discussion
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[Form] [ChoiceType] Add a `placeholder_attr` option

| Q             | A
| ------------- | ---
| Branch?       | 6.3
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Tickets       | #38958
| Similar Pull Request | #47570
| License       | MIT
| Doc PR        | symfony/symfony-docs#17469

Allow to custom the attributes of the placeholder (`data-*`, `title`, `disabled`, etc.).

Commits
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2d4396ad50 [Form][ChoiceType] Add placeholder_attr field option

Author: fabpot

Resources/views/Form/form_div_layout.html.twig

@@ -61,7 +61,7 @@
     {%- endif -%}
     <select {{ block('widget_attributes') }}{% if multiple %} multiple="multiple"{% endif %}>
         {%- if placeholder is not none -%}
-            <option value=""{% if required and value is empty %} selected="selected"{% endif %}>{{ placeholder != '' ? (translation_domain is same as(false) ? placeholder : placeholder|trans({}, translation_domain)) }}</option>
+            <option value=""{% if placeholder_attr|default({}) %}{% with { attr: placeholder_attr } %}{{ block('attributes') }}{% endwith %}{% endif %}{% if required and value is empty %} selected="selected"{% endif %}>{{ placeholder != '' ? (translation_domain is same as(false) ? placeholder : placeholder|trans({}, translation_domain)) }}</option>
         {%- endif -%}
         {%- if preferred_choices|length > 0 -%}
             {% set options = preferred_choices %}

Resources/views/Form/foundation_5_layout.html.twig

@@ -156,7 +156,7 @@
     {%- endif -%}
     <select {{ block('widget_attributes') }}{% if multiple %} multiple="multiple" data-customforms="disabled"{% endif %}>
         {% if placeholder is not none -%}
-            <option value=""{% if required and value is empty %} selected="selected"{% endif %}>{{ translation_domain is same as(false) ? placeholder : placeholder|trans({}, translation_domain) }}</option>
+            <option value=""{% if placeholder_attr|default({}) %}{% with { attr: placeholder_attr } %}{{ block('attributes') }}{% endwith %}{% endif %}{% if required and value is empty %} selected="selected"{% endif %}>{{ translation_domain is same as(false) ? placeholder : placeholder|trans({}, translation_domain) }}</option>
         {%- endif %}
         {%- if preferred_choices|length > 0 -%}
             {% set options = preferred_choices %}