Feature: #86881 - Support of Features in expression language

See Issue #86881

Description

With #83429 the core got support for feature toggles including a small API. This patch adds support for feature toggle check in the symfony expression language DefaultFunctionProvider. With the new function feature() the feature toggle can be checked.

[feature("TypoScript.strictSyntax")]
# This condition matches if the feature toggle "TypoScript.strictSyntax" is true
[END]

[feature("TypoScript.strictSyntax") === false]
# This condition matches if the feature toggle "TypoScript.strictSyntax" is false
[END]