bug #9327 [2.2][Form] Changed FormTypeCsrfExtension to use the form's name as default intention (bschussek)

This PR was merged into the 2.2 branch.

Discussion
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[2.2][Form] Changed FormTypeCsrfExtension to use the form's name as default intention

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Before, every form used the same "intention"/"csrf_token_id" value by default, namely "unknown". This PR fixes the default value to the form's name, which is at least different for forms with (a) explicit names and (b) different types, where the implicit name equals the type's name.

Commits
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b07c618 [Form] Changed FormTypeCsrfExtension to use the form's name as default intention
Fix docblock typo
minor #9312 [Security] Fix docblock typo (adrienbrault)

This PR was submitted for the master branch but it was merged into the 2.2 branch instead (closes #9312).

Discussion
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[Security] Fix docblock typo

Commits
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bff65b2 [Security] Fix docblock typo
[Intl] Improved FormTypeCsrfExtension to use the type class as default intention if the form name is empty