VReplication: Fix vtctldclient SwitchReads related bugs and move the TestBasicV2Workflows e2e test to vtctldclient

[mattlord]

Description

This work was originally done via #15536 as I only planned to do that work in the vtctldclient implementation and thus I needed to use vtctldclient in order to test the fix. In doing so, I saw other test failures when using the vtctldclient implementation and I fixed those there as well.

BUT, because I did not plan to backport that PR and it still remains to be seen how involved/intrusive a full fix may be and also when it will be ready, I'm moving the work not specifically related to that issue here so it can be pushed ASAP and backported to v18 (where the vreplication commands were first added to vtctldclient).

I would like to backport this to v18 so that we have the traffic switching fixes and so that we have better test coverage now that we want all users to use vtctldclient.

Related Issue(s)

• Fixes: Bug Report: vtctldclient implementation of SwitchReads is not working correctly #15594

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

[vitess-bot]

Review Checklist

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 32 lines in your changes are missing coverage. Please review.

Project coverage is 65.77%. Comparing base (696fe0e) to head (0548af7).
Report is 160 commits behind head on main.

Files	Patch %	Lines
go/vt/vtctl/workflow/traffic_switcher.go	0.00%	17 Missing ⚠️
go/vt/vtctl/workflow/server.go	0.00%	13 Missing ⚠️
...lient/command/vreplication/common/switchtraffic.go	0.00%	1 Missing ⚠️
go/vt/vttablet/tabletmanager/rpc_vreplication.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15579      +/-   ##
==========================================
- Coverage   67.41%   65.77%   -1.65%     
==========================================
  Files        1560     1561       +1     
  Lines      192752   194874    +2122     
==========================================
- Hits       129952   128183    -1769     
- Misses      62800    66691    +3891     

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[rohit-nayak-ps]

What changed that we don't need this code anymore? Are we initializing the source and target shards differently ?

[mattlord]

Nothing changed. It just wasn't correct. When building the traffic switcher in the vtctldclient implementation we determine the source and target based on the direction. So this was incorrectly doing something equivalent to what we do in the vtctlclient implementation, when we shouldn't be. It resulted in test failures.