If data already exists in a stackerdb slot, update version number

[jferrant]

Improvement to our version number logic. Do not increment by one. Just immediately update to one past the last seen version number.

Applicable issues

Closes #4506

[obycode]

lgtm!

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 71.92%. Comparing base (206ea63) to head (60c6abc).

Additional details and impacted files

@@             Coverage Diff             @@
##             next    #4507       +/-   ##
===========================================
- Coverage   83.24%   71.92%   -11.32%     
===========================================
  Files         452      452               
  Lines      326005   326008        +3     
  Branches      323      323               
===========================================
- Hits       271372   234492    -36880     
- Misses      54625    91508    +36883     
  Partials        8        8               

Files	Coverage Δ
stacks-signer/src/client/stackerdb.rs	89.79% <80.00%> (-0.29%)	⬇️

... and 214 files with indirect coverage changes

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