proxy: listen on additional addrs

[xhebox]

What problem does this PR solve?

Issue Number: close #392

Problem Summary: As title, requested by serverless team.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Notable changes

• Has configuration change
• Has HTTP API interfaces change
• Has tiproxyctl change
• Other user behavior changes

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

Support listening SQL server on multiple addrs

[xuanyu66]

@xhebox Could we also add the label port in gauge metrics?
https://github.com/pingcap/tiproxy/pull/393/files#diff-b41d02f71c670ff801d99892d32ef6dd36e43fcdf4c12c044cd34a073cc18200L165

[djshow832]

Rest LGTM

[djshow832]

I don't think we need to adapt to that: Gateway doesn't use TiProxy metrics.

[djshow832]

Oops, I just saw the comment #393 (comment)

[djshow832]

@xhebox Could we also add the label port in gauge metrics? https://github.com/pingcap/tiproxy/pull/393/files#diff-b41d02f71c670ff801d99892d32ef6dd36e43fcdf4c12c044cd34a073cc18200L165

Gateway doesn't use TiProxy metrics. Are you going to add the metrics in Gateway? @xuanyu66

[xuanyu66]

@djshow832 We want to see the traffic for each port. Do you mean that the gateway won't expose Tipoxy's metrics?
Even if the gateway doesn't use these metrics, this change is meaningful for other users.

[djshow832]

@djshow832 We want to see the traffic for each port. Do you mean that the gateway won't expose Tipoxy's metrics? Even if the gateway doesn't use these metrics, this change is meaningful for other users.

Yes, I mean Gateway doesn't expose those metrics and we have no way to see them.
This feature is only for Gateway. I don't think it's meaningful in other situations. @xuanyu66

[xuanyu66]

@djshow832 LGTM

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-11-03 06:51:05.846707877 +0000 UTC m=+3195063.433818022: ☑️ agreed by djshow832.

[ti-chi-bot]

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: djshow832, zhangyangyu

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