[TwigBundle] Deprecate option "autoescape", use "autoescape_service[_method]" instead

[nicolas-grekas]

Q	A
Branch?	6.1
Bug fix?	no
New feature?	no
Deprecations?	yes
Tickets	-
License	MIT
Doc PR	-

This option is a foot-gun, even the tests are wrong since true doesn't mean anything for it.
Also because eg disabling auto-escaping breaks forms / emails, which expect an html escaping strategy.

I therefore propose to deprecate option autoescape and to keep autoescape_service + autoescape_service_method, which are more capable, and will require ppl to think twice before returning false.

For ppl that need a custom escaping strategy, you'll likely want to use/take inspiration from FileExtensionEscapingStrategy::guess() in your implementation.

[fabpot]

Thank you @nicolas-grekas.