Update identity metrics with feedback

[JamesNK]

Based on feedback at open-telemetry/semantic-conventions#2508

Also pluralizes the counter names which makes them more consistent with other ASP.NET Core counters.

User metrics:

• Change aspnetcore.identity.user.create, aspnetcore.identity.user.update, aspnetcore.identity.user.delete names to have .duration suffix. Change from counters to histograms
• Rename aspnetcore.identity.user.check_password to aspnetcore.identity.user.check_password_attempts
• Rename aspnetcore.identity.user.verify_token to aspnetcore.identity.user.verify_token_attempts
• Rename aspnetcore.identity.user.generate_token to aspnetcore.identity.user.generated_tokens

Sign in metrics:

• Change aspnetcore.identity.sign_in.authenticate to aspnetcore.identity.sign_in.authenticate.duration and from counter to histogram
• Change aspnetcore.identity.sign_in.remember_two_factor to aspnetcore.identity.sign_in.two_factor_clients_remembered
• Change aspnetcore.identity.sign_in.forget_two_factor to aspnetcore.identity.sign_in.two_factor_clients_forgotten
• Change aspnetcore.identity.sign_in.check_password to aspnetcore.identity.sign_in.check_password_attempts
• Change aspnetcore.identity.sign_in.sign_in to aspnetcore.identity.sign_in.sign_ins
• Change aspnetcore.identity.sign_in.sign_out to aspnetcore.identity.sign_in.sign_outs

Metadata:

• Rename aspnetcore.identity.authentication_scheme to aspnetcore.authentication.scheme (shared with AuthN metrics)
• Rename aspnetcore.identity.sign_in.is_persistent to aspnetcore.authentication.is_persistent (in case AuthN metrics also records it)

[Copilot]

Pull Request Overview

This PR updates the ASP.NET Core Identity metrics with significant naming and type changes based on user feedback. The changes focus on converting timing operations from counters to histograms with duration suffixes, and renaming several metrics for clarity and consistency.

Key changes:

• Convert create/update/delete user operations from counters to histograms tracking duration
• Rename metrics to be more descriptive (e.g., adding "attempts" suffix for password checks)
• Update SignInManager metrics with better naming conventions

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/Shared/ValueStopwatch/ValueStopwatch.cs	Refactored timing logic to support duration measurements
src/Identity/test/Shared/MetricsHelpers.cs	Added helper method for validating duration metrics
src/Identity/test/Identity.Test/UserManagerTest.cs	Updated test assertions to validate histogram duration metrics
src/Identity/test/Identity.Test/SignInManagerTest.cs	Updated test metric collectors for renamed SignInManager metrics
src/Identity/Extensions.Core/src/UserUpdateType.cs	Renamed UserName enum value to SetUserName
src/Identity/Extensions.Core/src/UserManagerMetrics.cs	Converted counters to histograms and updated metric names
src/Identity/Extensions.Core/src/UserManager.cs	Added timestamp tracking for duration measurements
src/Identity/Extensions.Core/src/Microsoft.Extensions.Identity.Core.csproj	Added ValueStopwatch shared source reference
src/Identity/Core/src/SignInManagerMetrics.cs	Updated SignInManager metric names and types
src/Identity/Core/src/SignInManager.cs	Added timestamp tracking for authenticate duration
src/Identity/Core/src/Microsoft.AspNetCore.Identity.csproj	Added ValueStopwatch shared source reference

[MackinnonBuck]

Looks great!