[2.3][Form] Cleanup & fix phpdocs
minor #11358 [2.3][Form] Cleanup & fix phpdocs (stloyd)

This PR was merged into the 2.3 branch.

Discussion
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[2.3][Form] Cleanup & fix phpdocs

| Q             | A
| ------------- | ---
| Bug fix?      | kinda
| New feature?  | no
| BC breaks?    | no
| Tests pass?   | yes
| License       | MIT

This PR was done mostly cause of reports about invalid/not supported types/variables in phpstorm/scrutinizer-ci, and after I started fixing I noticed more problems in those phpdocs so I have cleanedup them a bit.

Commits
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a67bc76 [2.3][Form] Cleanup & fix phpdocs