Support for PRF Extension

[kspearrin]

This PR adds support for the PRF extension to the extension client input/output models.

All existing tests pass, but I am not sure if/what new tests need to be added for PRF support in this library.

[kspearrin]

@dotnet-policy-service agree company="Bitwarden"

[codecov-commenter]

Codecov Report

Merging #390 (a400af8) into master (5e72564) will decrease coverage by 0.05%.
The diff coverage is 62.50%.

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@@            Coverage Diff             @@
##           master     #390      +/-   ##
==========================================
- Coverage   76.80%   76.76%   -0.05%     
==========================================
  Files          89       92       +3     
  Lines        2531     2539       +8     
  Branches      427      427              
==========================================
+ Hits         1944     1949       +5     
- Misses        466      469       +3     
  Partials      121      121              

Impacted Files	Coverage Δ
...ls/Objects/AuthenticationExtensionsClientInputs.cs	16.66% <0.00%> (-3.34%)	⬇️
...odels/Objects/AuthenticationExtensionsPRFInputs.cs	0.00% <0.00%> (ø)
...s/Objects/AuthenticationExtensionsClientOutputs.cs	100.00% <100.00%> (ø)
...dels/Objects/AuthenticationExtensionsPRFOutputs.cs	100.00% <100.00%> (ø)
...odels/Objects/AuthenticationExtensionsPRFValues.cs	100.00% <100.00%> (ø)

[kspearrin]

Added a bit of testing to match what I see being done with other extension properties.