docs(metrics): clarify MetricsConfiguration metric names

[officialasishkumar]

Description

Clarifies that Advanced metrics documentation lists exported Prometheus metric names, while MetricsConfiguration uses base metric names in spec.contextOptions[].metricName.

Adds a mapping table for the Advanced metrics names, including the TCP retransmission case where the exported metric is adv_tcpretrans_count and the CRD value is tcp_retransmission_count.

Related Issue

Fixes #1999

Checklist

• I have read the contributing documentation.
• I signed and signed-off the commits (git commit -S -s ...). See this documentation on signing commits.
• I have correctly attributed the author(s) of the code.
• I have tested the changes locally.
• I have followed the project's style guidelines.
• I have updated the documentation, if necessary.
• I have added tests, if applicable.

Screenshots (if applicable) or Testing Completed

• npx --yes markdownlint-cli2 --config .github/.markdownlint.json 'docs/**/*.md'
• npm install --prefix site/ && npm run build --prefix site/

Additional Notes

No runtime changes are included.

[officialasishkumar]

@microsoft-github-policy-service agree

[SRodi]

thanks for this contribution @officialasishkumar ! Your signature/key needs to be verified, see steps here https://retina.sh/docs/Contributing/development#cryptographic-signing-of-commits