Add test case TC_GCAST_2_2 (project-chip#42880)

* Add test case TC_GCAST_2_2

* Complete test case TC_GCAST_2_2

* Implement updates for TC-GCAST-2.2 and common utils

* Sync TC_GCAST_common.py with Stefan's merged version

* Refactor TC-GCAST-2.2 to align with team patterns and spec updates

* Fixed test based on Tennessee's comments

* Addressed review comments

* Updated test based on github.com/project-chip/pull/43094

* Addressed jmartinez-silabs comments

* Revert openthread submodule

* Fix endpoint type casting for GCAST test and other comments from jmartinez-silabs

* Restyled by isort

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Co-authored-by: Restyled.io <commits@restyled.io>
Co-authored-by: Junior Martinez <67972863+jmartinez-silabs@users.noreply.github.com>

Author: 3 people