Fix/scale types for pending ceremonies

[martin-chainflip]

Pull Request

Closes: PRO-1676

Checklist

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

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

Summary

This change renames the types returned by the ThresholdSignature -> pendingCeremonies call so that different types have different names.

[codecov]

Codecov Report

Attention: Patch coverage is 93.93939% with 2 lines in your changes missing coverage. Please review.

Project coverage is 70%. Comparing base (a17fd16) to head (2134920).

Files with missing lines	Patch %	Lines
...te-chain/pallets/cf-threshold-signature/src/lib.rs	94%	2 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##            main   #5286    +/-   ##
======================================
- Coverage     70%     70%    -0%     
======================================
  Files        487     487            
  Lines      87295   87182   -113     
  Branches   87295   87182   -113     
======================================
- Hits       61312   61141   -171     
- Misses     22703   22759    +56     
- Partials    3280    3282     +2     

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