proxy: Exclude private ip errors from recorded metrics

[khanova]

Problem

Right now we record errors from internal VPC.

Summary of changes

• Exclude it from the metrics.
• Simplify pg-sni-router

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

[github-actions]

2748 tests run: 2630 passed, 0 failed, 118 skipped (full report)

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Flaky tests (1)

Postgres 14

• test_compute_pageserver_connection_stress: release

Code coverage* (full report)

• functions: 28.0% (6429 of 22940 functions)
• lines: 46.6% (45029 of 96589 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
cea9332 at 2024-04-15T16:28:15.531Z :recycle:}

[conradludgate]

Code change looks fine, just nit pick on the lockfile