metrics: set the Y axis of some metrics to logBase=2

[djshow832]

What problem does this PR solve?

Issue Number: close #542

Problem Summary:
Using log2 on the Y axis of some metrics is clearer, especially duration and CPS.

What is changed and how it works:
Update metrics json to add logBase=2.

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

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None

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: xhebox

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-06-19 04:55:28.682137933 +0000 UTC m=+177055.167626764: ☑️ agreed by xhebox.