[Cisco][G200/G202x] Device watermark test fixes for G200/G202x

[itskittycisco]

Pre-submission checklist

• I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
• pre-commit run
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Summary

1. G200/G202x/Q200 supports SAI_BUFFER_POOL_STAT_WATERMARK_BYTES. The test validates this after sending traffic.
2. After the port flap, it is expected to have a min buffer and hence add a minimum buffer value for G200/G202x. Q200 already had a check with min buffer value.
3. Exclude counter check for buffer_watermark_device.p100.60 that is not applicable for G200/G202x/Q200.

Test Plan

Verified running the test manually - AgentWatermarkTest.VerifyDeviceWatermark