feat(conntrack): make map max entries configurable

[mmckeen]

Description

Allows configuring the conntrack map maximum size, e.g. for systems tracking lots of connections.

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

Unit tests added, deployed with a custom size on a test cluster.

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[mmckeen]

Superseded by microsoft#2502 — re-targeted this change to the upstream microsoft/retina repo.