feat: btc vault swap with affiliates

[j4m1ef0rd]

Pull Request

Closes: PRO-1815

Checklist

Please conduct a thorough self-review before opening the PR.

• [x] I am confident that the code works.
• [x] I have written sufficient tests.
• [ ] I have written and tested required migrations.
• [ ] I have updated documentation where appropriate.

Summary

• Completed the encoding of the affiliates in the cf_get_vault_swap_details rpc.
• Added a RPC to the broker api to register an affiliate.
• Added an affiliate to the bouncer btc vault swap test.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 23.40426% with 108 lines in your changes missing coverage. Please review.

Project coverage is 72%. Comparing base (7beca6d) to head (518c3a8). Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
state-chain/runtime/src/lib.rs	8%	0 Missing and 49 partials :warning:
api/lib/src/lib.rs	0%	37 Missing :warning:
state-chain/traits/src/mocks/affiliate_registry.rs	9%	10 Missing :warning:
state-chain/pallets/cf-swapping/src/lib.rs	47%	9 Missing :warning:
engine/src/witness/arb.rs	0%	1 Missing :warning:
engine/src/witness/eth.rs	0%	1 Missing :warning:
state-chain/primitives/src/lib.rs	75%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #5413 +/- ## ====================================== - Coverage 72% 72% -0% ====================================== Files 490 490 Lines 86916 86876 -40 Branches 86916 86876 -40 ====================================== - Hits 62396 62234 -162 - Misses 21587 21692 +105 - Partials 2933 2950 +17 ```

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