Use file scoped namespaces

[iamcarbon]

This PR converts the remaining files to use file-scoped namespaces. There are no functional changes in this PR.

[iamcarbon]

@abergs @aseigler Ready for review / feedback.

[iamcarbon]

Consider reviewing while ignoring whitespace.

https://github.com/passwordless-lib/fido2-net-lib/pull/343/files?diff=split&w=1

[codecov-commenter]

Codecov Report

❌ Patch coverage is 77.69965% with 444 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.87%. Comparing base (dd727b1) to head (61a3590).

Files with missing lines	Patch %	Lines
Src/Fido2.Models/CredentialCreateOptions.cs	40.24%	47 Missing and 2 partials ⚠️
...c/Fido2/Metadata/Fido2MetadataServiceRepository.cs	60.39%	29 Missing and 11 partials ⚠️
Src/Fido2/Metadata/FileSystemMetadataRepository.cs	0.00%	34 Missing ⚠️
Src/Fido2.AspNet/Fido2NetLibBuilderExtensions.cs	0.00%	33 Missing ⚠️
Src/Fido2/ConformanceMetadataService.cs	0.00%	30 Missing ⚠️
Src/Fido2/AuthenticatorAssertionResponse.cs	49.12%	14 Missing and 15 partials ⚠️
Src/Fido2/Objects/CredentialPublicKey.cs	72.00%	20 Missing and 8 partials ⚠️
Src/Fido2/DevelopmentInMemoryStore.cs	0.00%	26 Missing ⚠️
Src/Fido2/Asn1Element.cs	67.79%	10 Missing and 9 partials ⚠️
...rc/Fido2.AspNet/DistributedCacheMetadataService.cs	84.21%	9 Missing and 6 partials ⚠️
... and 28 more

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #343   +/-   ##
=======================================
  Coverage   77.87%   77.87%           
=======================================
  Files          88       88           
  Lines        2495     2495           
  Branches      415      415           
=======================================
  Hits         1943     1943           
  Misses        439      439           
  Partials      113      113           

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[abergs]

LGTM 👍