Fix several network stats issues

[yibin87]

What problem does this PR solve?

Issue Number: ref #9748

Problem Summary:

What is changed and how it works?

Fix several issues for network traffic stats:

1. Two typo-like issues for mixing variable names. Previously, no tidb side changes, so only checks the remote coprocessor read code path manually, This time tests with tidb side changes, found these issues. RT.
2. Currently, in exchange sender side, we stats very small packets which don't look like data packets, with size <= 2 bytes; while in receiver side, these packets are not found. Maybe they include eof or other kinds of packets. Since they are so small that we can just ignore them now.
3. For fine grained shuffle exchange receiver, the network traffic is counted duplicatedly.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
  Manually test with executor,util: Stat inner/inter zone network traffic for MPP tasks tidb#58683, check execution summary values.
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

None

[windtalker]

lgtm

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: windtalker

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-01-14 08:24:36.396290084 +0000 UTC m=+20547.851336230: ☑️ agreed by windtalker.