Change all tests using v0.x.x flag format

[thomaspoignant]

Warning

As mention in the issue #2398 we have decided to drop the support of the v0.x.x flag format.
Before creating a pull request for that, please check in the main issue if is the right moment to do it.

Some tests are still using the v0 flag format and are not migrated to the v1 format.
To be able to drop completely the v0 format we need to be sure that all the tests are using the v1 format.

What should we do?

• Update all tests that are still using the v0 format to use the v1 format
• Remove tests used for format compatibility checks (ex: check that v0 and v1 are affecting users to the same variant)

[thomaspoignant]

/assign-me

[github-actions]

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