[Form] fix and unify phpdoc

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| license?      | MIT

- Fixes FormTypeGuesserInterface that must return ValueGuess for guessRequired etc. instead of abstract Guess because its excepted for example by FormFactory.
- Unify array typehints that was not done consistently.