Fix orchagent crash when destroying MuxAclHandler after AclOrch

[harjotsinghpawra]

Description of PR

Fixes an orchagent crash during shutdown when MuxAclHandler objects are
destroyed after AclOrch.

Summary:
Fixes # (issue)

Type of change

• Bug fix
• New feature
• Refactor / cleanup
• Documentation update
• Test improvement

Approach

What is the motivation for this PR?

MuxAclHandler attempted to access the global AclOrch instance after
AclOrch had already been destroyed. It could also throw when the expected
MUX ACL rule was unavailable during teardown.

How did you do it?

• Clear gAclOrch from AclOrch destructor.
• Skip ACL unbinding when AclOrch is already destroyed.
• Log and skip unbinding when the ACL rule is missing instead of throwing.
• Add a regression test for Mux teardown after ACL orchestrator destruction.

How did you verify/test it?

30c6ea5ff0e0:/sonic/src/sonic-swss/tests/mock_tests$ ./tests --gtest_filter='MuxRollbackTest.MuxTeardownAfterAclOrchDestructionIsSafe'
Running main() from ./googletest/src/gtest_main.cc
Note: Google Test filter = MuxRollbackTest.MuxTeardownAfterAclOrchDestructionIsSafe
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from MuxRollbackTest
[ RUN ] MuxRollbackTest.MuxTeardownAfterAclOrchDestructionIsSafe
[ OK ] MuxRollbackTest.MuxTeardownAfterAclOrchDestructionIsSafe (161 ms)
[----------] 1 test from MuxRollbackTest (161 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test suite ran. (161 ms total)
[ PASSED ] 1 test.

Any platform specific information?

N/A

Documentation

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[mssonicbld]

/azp run

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[Ndancejic]

Hi @harjotsinghpawra, there is a PR that addresses this already. Please help review/test to confirm this fix works for you. #4830

[mssonicbld]

Hi, there are workflow run(s) waiting for approval, you may be first-time contributor. I will notify maintainers to help approve once PR is approved. Thanks!

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[prsunny]

Closing this in favor of #4830