Add mechanism to load v0.22.3 snapshots on newer Solana versions

[mvines]

Once #7801 lands, snapshots produced by v0.22.3 (ie, version that SLP was running) will not be loadable on v0.22.4. As a stopgap measure until #7738:

1. Add a version text file to the snapshot archive. Snapshots without this version file are assumed to be "v0.22.3"-based.
2. Snapshots that are of the same version as the currently running code are compatible
3. Snapshots that are "v0.22.3"-based can be loaded on new versions using a LegacyBank0223 struct

NB: This will be landed on v0.22 first then cherry-picked up to master

[mvines]

@ryoqun - what do you think?

[codecov]

Codecov Report

Merging #7917 into v0.22 will decrease coverage by 16%.
The diff coverage is 4.1%.

@@           Coverage Diff            @@
##           v0.22   #7917      +/-   ##
========================================
- Coverage   80.9%   64.9%   -16.1%     
========================================
  Files        243     243              
  Lines      51790   64573   +12783     
========================================
+ Hits       41943   41948       +5     
- Misses      9847   22625   +12778