[type-declaration-docblock] kick of docblock rules to help with iterables

[TomasVotruba]

No description provided.

[samsonasik]

I think the DocblockGetterReturnArrayFromPropertyDocblockVarRector should avoid mixed:

@return mixed[]

or

@return mixed[]|null

as possible, use scalar, iterable, and objects is probably better imo.

[TomasVotruba]

@samsonasik Agreed, we can add mixed[] rule as the very last one, after everything else is applied.
Feel free to add PR to skip it, if mixed[] or mixed[]|null

[samsonasik]

#7261