cmd, sqlreplay: add service mode and support to set address in replay config

[YangKeao]

What problem does this PR solve?

Issue Number: close #970

Problem Summary:

What is changed and how it works:

1. Add a service mode for replayer, which will do nothing but wait for the API call.
2. Allow to set the addr in replay config.

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.

None

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 24.61538% with 49 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@358165b). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
cmd/replayer/main.go	0.00%	31 Missing ⚠️
pkg/proxy/backend/static_handshake_handler.go	0.00%	18 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #971   +/-   ##
=======================================
  Coverage        ?   67.51%           
=======================================
  Files           ?      137           
  Lines           ?    13634           
  Branches        ?        0           
=======================================
  Hits            ?     9205           
  Misses          ?     3790           
  Partials        ?      639           

Flag	Coverage Δ
unit	67.51% <24.61%> (?)

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[YangKeao]

/hold

Maybe @Daemonxiao can verify this PR before we review / merge it.