This commit removes the following 22.1 version gates:

• PebbleFormatBlockPropertyCollector
• PebbleFormatSplitUserKeysMarked

Cleanup was done following guidance from 21.2 cleanup:

For the most part, if the gates were just simple if !version.IsActive { return x } or something, I just removed the block, and even if it was a little more complicated, like args = [x]; if version { args = append(args, y) }; foo(args) I still tried to mostly inline it such that it looked natural (i.e. remove that append and make it args = [x, y]).

However for just a couple more complicated cases that were referring to <21.2 versions that needed to be replaced when those were deleted, I added a placeholder clusterversion.TODOPre21_2 alias for 21.2. Replacing those calls with this alias shouldn't change their behavior -- it was already always true, since the code today should never run in a <21.2 cluster -- but means we can delete those older versions in the meantime and then the owners of these bits can decide how to update them.

Partially addresses #80663

Release note: none