[TF-M] TFM_VERSION

I notice that TFM_VERSION_MANUAL gets set to "2.2.1" in both release/2.2.x and in main. Granted, the hash gets appended to make TFM_VERSION, and there's some reading of git tags involved that can override TFM_VERSION_MANUAL, but it still feels odd that both identify as the "same" version.

Perhaps main should be flagged as being the "next" version as soon as the previous version branch has been created? So we would tag main as v2.3.pre or something. Either that or something that identifies as *not* being a regular release.

Chris