[platform_tests/counterpoll]: Support multi-asic for counterpoll watermark tests

[liamkearney-msft]

• Update counterpoll watermark platform test to support multi-asic DUTs

BugLink: #14753

Description of PR

Refactor test_counterpoll_watermark to properly handle multi-asic DUTs. The previous version of the test would fail on multi-asic as it would not look at the namespaced database containers.

Summary:
Fixes #14753

Type of change

• [x ] Bug fix
• Testbed and Framework(new/improvement)
• [ x] Test case(new/improvement)

Back port request

• 202012
• 202205
• 202305
• 202311
• 202405

Approach

What is the motivation for this PR?

Fix test case to properly run on multi-asic

How did you do it?

How did you verify/test it?

Ran the test on a testbed with multi-asic and single asic devices. Test runs without errors in testplan logic

Any platform specific information?

Supported testbed topology if it's a new test case?

Documentation

[mssonicbld]

The pre-commit check detected issues in the files touched by this pull request.
The pre-commit check is a mandatory check, please fix detected issues.

Detailed pre-commit check results:
trim trailing whitespace.................................................Passed
fix end of files.........................................................Passed
check yaml...........................................(no files to check)Skipped
check for added large files..............................................Passed
check python ast.........................................................Passed
flake8...................................................................Failed
- hook id: flake8
- exit code: 1

tests/platform_tests/counterpoll/counterpoll_helper.py:4:1: E302 expected 2 blank lines, found 1

flake8...............................................(no files to check)Skipped
check conditional mark sort..........................(no files to check)Skipped

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