config: skip irrelevant config file events

[djshow832]

What problem does this PR solve?

Issue Number: close #321

Problem Summary:

• If the log file is in the same directory as the config file, TiProxy reloads the config file once the log outputs, and reloading itself causes log output, which is a dead loop.
• If the directory is removed and then both the directory and the file are created within 200ms, the ConfigManager doesn't receive an event.

What is changed and how it works:

• Check the file name for the watch event
• Reload events if watch list is empty before adding
• Support searching logger for test

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

[xhebox]

Test failed

[xhebox]

Rest LGTM

[xhebox]

There is a need to removing and recreating the file

[djshow832]

Addressed.