[9.x] Improves Support\Collection and Database\Eloquent\Collection type definitions (#38538)

* Adds CI workflow

* Adds phpstan

* Adds work in progress regarding generic collections

* Fixes missing template

* Renames template

* Updates test

* Apply fixes from StyleCI

* Adds work in progress regarding generic collections

* Adds work in progress regarding generic collections

* Adds work in progress regarding generic collections

* Adds work in progress regarding generic collections

* Adds work in progress regarding generic collections

* Styling

* Apply fixes from StyleCI

* Apply fixes from StyleCI

* Adds work in progress regarding generic collections

* Remove work on Models

* Revert "Remove work on Models"

This reverts commit d6c42910a032f1647f07d42dc800d8be22a77963.

* Removes `prefer-lowest`

* Removes non needed code on CI job

Co-authored-by: Dries Vints <dries@vints.io>

* Fixes `Eloquent\Collection::load` types

* Adds work in progress regarding generic collections

* Fixes `Eloquent\Collection::load` related methods

Co-authored-by: Taylor Otwell <taylorotwell@users.noreply.github.com>
Co-authored-by: Dries Vints <dries@vints.io>

Author: 3 people