Update ClusterMarker doc strings to clarify versioning requirements

[pcholakov]

This PR updates the version compatibility tuple for the Restate 1.1.0 release.

• Since we are not introducing new default features that break backwards compatibility with prior releases, the minimum forwards-compatible version remains at 1.0.0.
• Since we are remain backwards-compatible with older versions' data stores, the minimum version which we can open with the new release also remains at 1.0.0.

I updated some comments which I feel make them easier to understand.

Fixes #1924

[github-actions]

Test Results

15 files  ±0  15 suites  ±0   20m 29s ⏱️ +22s
 6 tests ±0   6 ✅ ±0  0 💤 ±0  0 ❌ ±0 
18 runs  ±0  18 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 62a6867. ± Comparison against base commit 539453e.

♻️ This comment has been updated with latest results.