Cache uncached AppContext.TryGetSwitch calls

[pavelsavara]

Fixes #66280

AppContext.TryGetSwitch involves a dictionary lookup on every call. Several call sites in the repo were not caching the result, causing repeated lookups on hot paths (e.g., per-request in middleware).

This PR caches all previously-uncached AppContext.TryGetSwitch calls into static readonly fields or static auto-property initializers ({ get; } =), so the switch is read once at static initialization time.

Breaking change

If someone was calling AppContext.SetSwitch on the feature switches during execution, this is a breaking change.

I think that those features are designed to be configured at compile time and not changed during execution.
I'm advocating to make this breaking change.

Changes

Server-side (no trimmer interaction)

• AuthorizationMiddleware — cached Microsoft.AspNetCore.Authorization.SuppressUseHttpContextAsAuthorizationResource into a static readonly bool field. This was the most impactful case since it ran on every HTTP request through the authorization pipeline.
• SignInManager<TUser> — cached Microsoft.AspNetCore.Identity.CheckPasswordSignInAlwaysResetLockoutOnSuccess into a static readonly bool field.
• DefaultEditorTemplates — cached Switch.Microsoft.AspNetCore.Mvc.UsePasswordValue into a static readonly bool field.

Components (trimmer/NAOT/WASM-safe)

These properties already had [FeatureSwitchDefinition] attributes or ILLink substitution entries, which let the trimmer replace the getter with a constant. The change from expression-bodied (=>) to auto-property initializer ({ get; } =) caches the value at runtime (when not trimmed) without affecting trimmer behavior.

• RemoteNavigationManager._throwNavigationException
• HttpNavigationManager._throwNavigationException
• HotReloadManager.IsSupported (shared source, compiled into 6 assemblies)
• RegexConstraintSupport.IsEnabled

[Copilot]

Pull request overview

This PR improves runtime performance by caching previously-uncached AppContext.TryGetSwitch feature switch reads so hot paths avoid repeated dictionary lookups. It updates a few server/identity/mvc code paths, and adjusts Components feature-switch patterns (including tests) to keep the same behaviors while avoiding per-call switch checks.

Changes:

• Cache AppContext.TryGetSwitch results into static fields/properties for Authorization middleware, Identity sign-in, and MVC editor templates.
• Convert several Components feature-switch checks to cached statics while preserving trimming/linker substitution behavior.
• Update affected tests to override cached values via reflection.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Security/Authorization/test/AuthorizationMiddlewareTests.cs	Updates test to force cached AuthorizationMiddleware switch value via reflection.
src/Security/Authorization/Policy/src/AuthorizationMiddleware.cs	Caches the authorization resource compat switch in a static field to avoid per-request lookups.
src/Mvc/Mvc.ViewFeatures/src/DefaultEditorTemplates.cs	Caches the password editor template switch in a static field.
src/Identity/Core/src/SignInManager.cs	Caches the lockout-reset switch to avoid repeated lookups during sign-in.
src/Components/Shared/src/HotReloadManager.cs	Caches hot reload support switch into a mutable static for test override + feature switch definition.
src/Components/Server/src/Circuits/RemoteNavigationManager.cs	Caches navigation exception switch using an auto-property initializer.
src/Components/Endpoints/test/EndpointHtmlRendererTest.cs	Updates navigation-related test to override cached switch value via reflection.
src/Components/Endpoints/src/DependencyInjection/HttpNavigationManager.cs	Caches navigation exception switch in a mutable static for test override + feature switch definition.
src/Components/Components/test/RendererTest.cs	Updates hot reload test to override cached switch value via reflection.
src/Components/Components/src/Routing/RegexConstraintSupport.cs	Caches regex constraint switch using an auto-property initializer.

[dariatiurina]

Added the same pattern that was introduced in PR to newly merged QuickGridFeatureFlag.