[BACKPORT] set vreplication net read and net write timeout session vars to high values #14203

[pjambet]

Description

Attempt at backporting vitessio#14203

Changes made:

• tablestreamer.go doesn't exist in v15, it was introduced later on: MoveTables: allow copying all tables in a single atomic copy phase cycle vitessio/vitess#13137, so changes were ignored
• the existing flags.go was not available in rowstreamer, so a new file, matching the one in main was created
• the test file doesn't exist so changes were dropped
• everything else was kept

Related Issue(s)

This would hopefully help with https://github.com/Shopify/vitess-project/issues/577

Checklist

• "Backport to:" labels have been added if this change should be back-ported
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on the CI
• Documentation was added or is not required

Deployment Notes

[austenLacy]

We tested the image in staging, but it's difficult to reproduce the error so we haven't been able to test if the fix actually improves reliability of migrations without releasing to the wild.

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[github-actions]

This PR was closed because it has been stale for 7 days with no activity.