feat: introduce miden-multisig-client

[MCarlomagno]

• First implementation of miden-multisig-client supporting:
  • transaction proposals
    • creation
    • signing
    • execution
    • psm coordination
    • offline coordination (import/export into files)
  • transaction types
    • create_p2id_note
    • consume_notes
    • add_signer
    • remove_signer
    • switch_psm
• Update and simplify demo using miden-multisig-client

[codecov-commenter]

Codecov Report

❌ Patch coverage is 21.64839% with 2215 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.60%. Comparing base (7bc139d) to head (a3a33b7).

❌ Your patch status has failed because the patch coverage (21.64%) is below the target coverage (90.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #72       +/-   ##
===========================================
- Coverage   74.34%   55.60%   -18.74%     
===========================================
  Files          43       66       +23     
  Lines        5125     7952     +2827     
===========================================
+ Hits         3810     4422      +612     
- Misses       1315     3530     +2215     

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