Prepare the release-2.7 branch

[frouioui]

Description

This Pull Request updates the release-2.7 branch to prepare it for the future releases of 2.7.*. It is part of the changes required to adopt a new release workflow that includes release branches.

It changes the version.go file and reverts the recent changes to vtorc tests (#282, #283) and the upgrade of dependencies (#280). The Pull Request #281 is also reverted.

@GuptaManan100, I have reverted the above Pull Request to restore the branch to its state when releasing v2.7.1. I have left the most recent changes to VTAdmin: #278 and #279. Let me know if this is an issue.

Changes that are reverted

• Upgrade Vitess dependency to 14.0.0 #280
• Remove removed flag in vttablet #281
• Introduce Durability Policy in VTop #282
• Augment VTAdmin test to also test VTOrc setup #283

Changes that are kept

• Reduce Vtadmin test flakiness #278
• VTAdmin cluster-config cleanup #279

[Verolop]

lgtm with the changes to restore the branch to the previous state, so I'll approve it, but would also be great to have @GuptaManan100 's +1 for the VTAdmin PRs

[GuptaManan100]

@frouioui Shouldn't we start the branch with the tagged version 2.7 and just change the version information there. Then we know that the branch would be at exactly the state that we did the release on. We should then backport the relevant PRs. Just my thoughts on the matter, this is fine too. I'll add the vtorc test again though on that branch, just to be sure that works.
The test will require to be altered a little bit though, since VTOp doesn't do SetKeyspaceDurabilityPolicy in that version

[frouioui]

@GuptaManan100, I agree, this is a similar logic here. The two PRs #278 & #279 are already "backported"/included.

[GuptaManan100]

Okay! Great