#2341 AcceptanceTests project xUnit v3 migration

[methran1304]

Closes #2341

• Migrate testing projects to xUnit.net v3 #2341

This PR introduces xUnit v2 to v3 package upgrade for AcceptanceTests project only.

Proposed Changes

• Added xunit.v3 package reference.
• Removed xunit v2.9.3.
• Removed xunit.SkippableFact as xUnit v3 has native support for skipping tests.
• Replaced Skip.If() with Assert.SkipWhen().
• Replaced Skip.IfNot() with Assert.SkipUnless().
• Updated Xunit.Abstractions to Xunit namespace (moved in v3)
• Improved test clarity by adding required reason string to skip assertions.

Docs: Migration v2 to v3

[raman-m]

Please move this code to the previous PR #2356 by cherry-picking the commits from the feature branch into the PR #2356 branch. Once that is done, go ahead and close this PR.

[raman-m]

Check the latest build status❗
The code in the feature branch isn't compiling due to build errors. How were the migrated projects tested if they couldn't be built? I've marked this PR as a draft.

[methran1304]

Check the latest build status❗ The code in the feature branch isn't compiling due to build errors. How were the migrated projects tested if they couldn't be built? I've marked this PR as a draft.

It was due a change in UnitTests project as I used find all and replace in the whole solution instead of just this project by mistake. As for the testing, I didn't try to build UnitTests project due to the scope of the changes. It's fixed now in this branch, I'll cherry-pick the commits into #2356 and close this now.