Rename ServerDomain -> RPID

[abergs]

This PR renames the configuration properties ServerDomain and ServerName to the more spec aligned RPID and RPName.

This library aims to be close to the spec in naming, and having these two fields be anything different is just confusing.

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 78.63%. Comparing base (2a19063) to head (3772484).
⚠️ Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
Src/Fido2.Models/CredentialCreateOptions.cs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #641      +/-   ##
==========================================
+ Coverage   78.37%   78.63%   +0.25%     
==========================================
  Files          98       98              
  Lines        2539     2546       +7     
  Branches      422      423       +1     
==========================================
+ Hits         1990     2002      +12     
+ Misses        439      434       -5     
  Partials      110      110              

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