What problem does this PR solve?

Issue Number: ref #642

Problem Summary:
There are some cases when users want to capture the traffic on the production cluster and replay the traffic on a testing cluster:

• A new TiDB version may have compatibility breakers, such as the statements failing, running slower, or resulting in different query results.
• When the cluster runs unexpectedly, users want to capture the traffic so that they can investigate it later by replaying the traffic.
• Test the maximum throughput of a scaled-up or scaled-down cluster using the real production workload instead of standard bench tools.

What is changed and how it works:
This proposes a design of capturing traffic on the production cluster and replaying the traffic on a testing cluster to verify the SQL compatibility and performance of the new cluster.

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