backend, net: reduce memory allocation in forwarding packets

[djshow832]

What problem does this PR solve?

Issue Number: close #381

Problem Summary:

• We can further avoid memory allocation through ForwardUntil for more kinds of packets, such as the OK packet.
• We don't need the affected rows and insert ids in the OK packets, while they are parsed and allocated memory.

What is changed and how it works:

• Use ForwardUntil in forwardPrepareCmd, forwardQueryCmd, and forwardResultSet.
• Support forwarding long data (length > 16MB) in ForwardUntil.
• Only return the server status in handleOKPacket and ignore other fields.
• Do not flush the data every time in load local infile because we have a fixed buffer anyway.

Check List

Tests

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

Performance tests:

• The benchmark result of BenchmarkForwardUntil is close to BenchmarkForwardWithReadWrite when loops<=10 but it becomes much better when loops>100.
• QPS of oltp_point_select is from 66305 to 67634. The effect is very little but it's better anyway.

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

[djshow832]

/retest

[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:

• 2023-11-06 07:32:29.737475939 +0000 UTC m=+3456747.324586068: ☑️ agreed by xhebox.
• 2023-11-06 07:32:36.969160283 +0000 UTC m=+3456754.556270429: ✖️🔁 reset by xhebox.
• 2023-11-06 07:52:17.466692554 +0000 UTC m=+3457935.053802684: ☑️ agreed by xhebox.