PHPStan level 6

[franmomu]

Subject

Adds more specific phpdoc types, I've marked as minor because it was more adding missing types, but if you think patch is fine, it can be changed.

There are two commits because I'm not sure about the second one. It's necessary because AuditReader is generic, but I'm not sure if the whole class should be generic or only some of the method 🤔

I am targeting this branch, because these changes are BC.

Changelog

### Fixed
- Specify iterable types

[franmomu]

I guess this means that when calling AuditManager::createAuditReader() would be always of type object and calling then for example AuditReader::find(Foo::class) would always return an object of type object instead of a Foo object

[VincentLanglet]

#488 (comment) might be a good way to solve this and still keep the generic

[franmomu]

I've created #488 since raising PHPStan level after this to level 7 shows 131 errors (vs. 23 in #488), example of errors:

------ ------------------------------------------------------
  Line   tests/CoreTest.php
 ------ ------------------------------------------------------
  118    Call to an undefined method object::getId().
  119    Call to an undefined method object::getName().
  126    Call to an undefined method object::getId().
  127    Call to an undefined method object::getName().
  128    Call to an undefined method object::getTailLength().
  135    Call to an undefined method object::getId().
  136    Call to an undefined method object::getName().
  137    Call to an undefined method object::getColor().
  252    Call to an undefined method object::getAuthor().
  274    Call to an undefined method object::getProfile().
 ------ ------------------------------------------------------

 ------ -----------------------------------------------------
  Line   tests/Issue/Issue111Test.php
 ------ -----------------------------------------------------
  47     Call to an undefined method object::getDeletedAt().
 ------ -----------------------------------------------------

 ------ --------------------------------------------------------------
  Line   tests/Issue/Issue196Test.php
 ------ --------------------------------------------------------------
  50     Call to an undefined method object::getSqlConversionField().
 ------ --------------------------------------------------------------

 ------ -------------------------------------------------
  Line   tests/Issue/Issue198Test.php
 ------ -------------------------------------------------
  50     Call to an undefined method object::getOwner().
  53     Call to an undefined method object::getOwner().
 ------ -------------------------------------------------

 ------ -------------------------------------------------------------------------
  Line   tests/Issue/Issue308Test.php
 ------ -------------------------------------------------------------------------
  49     Cannot call method getRev() on SimpleThings\EntityAudit\Revision|false.
  51     Call to an undefined method object::getChildren().
 ------ -------------------------------------------------------------------------

 ------ --------------------------------------------------------
  Line   tests/Issue/Issue87Test.php
 ------ --------------------------------------------------------
  58     Call to an undefined method object::getOrganisation().
  59     Call to an undefined method object::getTitle().
  60     Call to an undefined method object::getSomeProperty().
  63     Call to an undefined method object::getProject().
  69     Call to an undefined method object::getProject().
 ------ --------------------------------------------------------

 ------ ----------------------------------------------------
  Line   tests/Issue/Issue9Test.php
 ------ ----------------------------------------------------
  52     Call to an undefined method object::getCustomer().
 ------ ----------------------------------------------------

 ------ --------------------------------------------------------------
  Line   tests/Issue/IssueConvertToPHPTest.php
 ------ --------------------------------------------------------------
  50     Call to an undefined method object::getSqlConversionField().
 ------ --------------------------------------------------------------

 ------ ------------------------------------------------------------
  Line   tests/RelationTest.php
 ------ ------------------------------------------------------------
  140    Call to an undefined method object::getOwned1().
  141    Call to an undefined method object::getOwned2().
  142    Call to an undefined method object::getOwner().
  183    Call to an undefined method object::getOwned1().
  226    Call to an undefined method object::getTitle().
  ...
 ------ ------------------------------------------------------------

[VincentLanglet]

Closing in favor of #488