[2.2][Form] Improved FormTypeCsrfExtension to use the type class as default intention if the form name is empty

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

ping @stof

follow-up PR to #9327