Wallet: Cache keysets

[callebtc]

accept new keyset id calculation, cache keysets, remove duplicate representations

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (1149533) 69.23% compared to head (edd3d31) 69.19%.

❗ Current head edd3d31 differs from pull request most recent head 09e7d52. Consider uploading reports for the commit 09e7d52 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #333      +/-   ##
==========================================
- Coverage   69.23%   69.19%   -0.04%     
==========================================
  Files          52       52              
  Lines        4212     4214       +2     
==========================================
  Hits         2916     2916              
- Misses       1296     1298       +2     

Files	Coverage Δ
cashu/wallet/wallet.py	88.92% <88.00%> (-0.33%)	⬇️

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.