Fix runtime bugs & add TryBindConfiguration / IServiceCollection.RegisterAzureStorage

[Copilot]

Three latent runtime bugs fixed and two developer-experience additions to align patterns across packages.

Bug fixes

• PersistentService.SaveOnBlobAsync — mutated metadatas dictionary while iterating it (guaranteed InvalidOperationException); also called fire-and-forget SetMetadata instead of await SetMetadataAsync. Fixed by projecting to a new dictionary and awaiting the async overload.
• IHttpContextAccessorExtensions.GetClaims — called Convert.FromBase64String on a potentially empty/missing header value, then dereferenced the deserialized result without null-checking. Now returns Enumerable.Empty<UserClaim>() on missing token or failed deserialization.
• RequireDaprApiTokenAttribute — cached the expected token in static fields (_expectedToken / _initialized), making the token stale across test runs and introducing a startup race. Now reads from IConfiguration per-request via the scoped IServiceProvider.

New APIs

TryBindConfiguration<T> — optional-section variants of BindConfiguration<T> on both IHostApplicationBuilder and IServiceCollection. Silent no-op when the section is absent rather than throwing.

// Does not throw if "FeatureX" is absent from appsettings
builder.TryBindConfiguration<FeatureXSettings>("FeatureX");
builder.TryBindConfiguration<FeatureXSettings>(out var featureX, "FeatureX");

IServiceCollection.RegisterAzureStorage — direct IServiceCollection overload mirroring the existing RegisterCosmosDb(IServiceCollection, IConfiguration, TokenCredential) pattern. The IHostApplicationBuilder variant now delegates to it.

// Usable in test hosts, Worker Services, etc. without IHostApplicationBuilder
services.RegisterAzureStorage(configuration, new DefaultAzureCredential());

Docs

Corrected misleading "Bing configuration object on section" summaries and added missing <typeparam>/<returns> XML doc tags across StartupRegistersExtensions.