Feature: #107105 - Introduce expression for accessing site locale 

See forge#107105

Description 

A new Symfony ExpressionLanguage expression locale() has been introduced.

This expression allows integrators and developers to directly access the current site locale, which is provided as a locale object. All public methods of this object are available for use.

For more information, refer to the API documentation: API

Example 

Using locale() in TypoScript conditions 
[locale().getName() == "en-US"]
    page.20.value = bar
[END]
[locale().getCountryCode() == "US"]
    page.30.value = foo
[END]
[locale().isRightToLeftLanguageDirection()]
    page.40.value = bar
[END]
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Using locale() in a form variant definition 
variants:
  - identifier: language-variant-1
    condition: 'locale().getName() == "en-US"'
    label: 'First name'
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Impact 

Developers can now compare or evaluate the site locale directly in expressions, without using siteLanguage("locale").