Add tests for BEiT

[sgligorijevicTT]

Ticket

Problem description

We need more tests

What's changed

I added a test for BEiT family of models

Checklist

• New/Existing tests provide coverage for changes

[github-actions]

	Tests	Passed ✅	Skipped ⚠️	Failed
TT-XLA Tests	483 ran	392 passed	91 skipped	0 failed

Test	Result
No test annotations available

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.46%. Comparing base (83c3808) to head (a140a16).
Report is 2 commits behind head on main.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #230   +/-   ##
=======================================
  Coverage   77.46%   77.46%           
=======================================
  Files          21       21           
  Lines        1025     1025           
=======================================
  Hits          794      794           
  Misses        231      231           

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