Add Passwordless.AspNetCore registration overloads that support IConfiguration properly

[Tyrrrz]

This PR fixes an issue where, when registering the Passwordless Identity integration, the core options (PasswordlessOptions) were not initialized with reload-tracking, due to the fact that the SDK was registered with services.AddPasswordlessSdk(_ => {}). Even though we forwarded the options by re-registering them inside the Identity integration, this did not forward the corresponding reload token.

I also added a few tests for configuration-related scenarios, although properly e2e testing configuration routing is quite challenging.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 34 lines in your changes missing coverage. Please review.

Project coverage is 59.82%. Comparing base (540def1) to head (f254967).

Files	Patch %	Lines
...sswordless.AspNetCore/IdentityBuilderExtensions.cs	43.10%	33 Missing ⚠️
src/Passwordless/ServiceCollectionExtensions.cs	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #146      +/-   ##
==========================================
- Coverage   61.39%   59.82%   -1.58%     
==========================================
  Files          43       43              
  Lines         658      687      +29     
  Branches       56       56              
==========================================
+ Hits          404      411       +7     
- Misses        250      272      +22     
  Partials        4        4              

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