Splitting main/dev: Add historic release-clmX.Y tags

We could add `release-clmX.Y` tags onto the new `main` branch going back some number of releases. Or maybe we could branch `main` from `master` at the 4.5 release, then do merges and tags for each release since then.

Existing minor version releases and the tags they correspond to:
- CLM4.5: [`clm4_5_18_r275`](https://github.com/ESCOMP/CTSM/releases/tag/clm4_5_18_r275)? That's the last release tag that has `clm4_5` in it.
- CLM5.0: [`clm5.0.000`](https://github.com/ESCOMP/CTSM/releases/tag/clm5.0.000)? [`release-clm5.0.01`](https://github.com/ESCOMP/CTSM/releases/tag/release-clm5.0.01)? [`release-clm5.0.03`](https://github.com/ESCOMP/CTSM/releases/tag/release-clm5.0.03)?
- CLM5.1: ?
- CLM5.2: [`ctsm5.2.005`](https://github.com/ESCOMP/CTSM/releases/tag/ctsm5.2.005)
- CLM5.3: [`ctsm5.3.021`](https://github.com/ESCOMP/CTSM/releases/tag/ctsm5.3.021)

**SE meeting 2025-11-20: Just 5.2 and 5.3 (and 5.4 if this doesn't happen until after that release).**