[action] [PR:15927] [YANG] add MUX_LINKMGR|SERVICE_MGMT

[mssonicbld]

Adding yang model for CONFIG_DB table MUX_LINKMGR|SERVICE_MGMT.

sign-off: Jing Zhang [email protected]

Why I did it

Work item tracking

• Microsoft ADO (number only): 18445751

How I did it

How to verify it

==================================================================================== test session starts ====================================================================================
platform linux -- Python 3.9.2, pytest-6.0.2, py-1.10.0, pluggy-0.13.0
rootdir: /sonic/src/sonic-yang-models
plugins: pyfakefs-5.2.3, cov-2.10.1
collected 3 items 

tests/test_sonic_yang_models.py .. [ 66%]
tests/yang_model_tests/test_yang_model.py . [100%]

===================================================================================== 3 passed in 2.06s =====================================================================================

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111
• 202205
• 202211
• 202305

Tested branch (Please provide the tested image version)

Description for the changelog

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)

[mssonicbld]

Original PR: #15927

[mssonicbld]

/azp run Azure.sonic-buildimage

[azure-pipelines]

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