Use SearchValues/ContainsAny/span helpers in more places

[MihaZupan]

I had Copilot look for more replaceable patterns, feel free to revert any where you don't think it matters.

[Copilot]

Pull request overview

This PR applies a set of low-risk micro-refactors across shared infrastructure and middleware/components code to use newer SearchValues<T>, ContainsAny* helpers, and span-based APIs, with the goal of improving readability and (in some cases) performance via vectorized implementations.

Changes:

• Replaced several IndexOfAny* / manual-loop patterns with ContainsAny*, Count(...), CopyTo(...), and Clear() span helpers.
• Introduced HttpRuleParser.IsToken(...) and updated token validations to use it consistently.
• Switched a few small char-set definitions to SearchValues<char> (with conditional compilation where multi-targeting requires it).

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/Shared/ServerInfrastructure/HttpCharacters.cs	Uses ContainsAnyExcept for authority validation against SearchValues<byte>.
src/Shared/HttpRuleParser.cs	Adds IsToken(...) helper based on ContainsAnyExcept(TokenChars).
src/Servers/Kestrel/shared/PooledStreamStack.cs	Replaces element-shifting/clearing loops with span CopyTo + Clear.
src/Mvc/Mvc.TagHelpers/src/GlobbingUrlBuilder.cs	Uses SearchValues<char> + Contains for HTML attribute whitespace checks.
src/Middleware/ResponseCaching/src/ResponseCachingKeyProvider.cs	Uses ContainsAny for delimiter detection.
src/Middleware/OutputCaching/src/OutputCacheKeyProvider.cs	Uses ContainsAny for delimiter detection.
src/Middleware/HttpOverrides/src/ForwardedHeadersMiddleware.cs	Uses ContainsAnyExcept* span helpers for scheme/port validation.
src/Http/Routing/src/Patterns/RoutePatternParser.cs	Uses ContainsAny for invalid parameter name character detection.
src/Http/Routing/src/Patterns/RoutePatternFactory.cs	Uses ContainsAny for invalid parameter name character detection.
src/Http/Routing/src/PathTokenizer.cs	Uses span Count('/') to compute segment count.
src/Http/Headers/src/HeaderUtilities.cs	Uses HttpRuleParser.IsToken and span Count for quoted-string escaping.
src/Http/Headers/src/CookieHeaderValue.cs	Uses HttpRuleParser.IsToken for cookie name validation.
src/Http/Headers/src/ContentDispositionHeaderValue.cs	Uses IsToken, ContainsAny, and ContainsAnyExceptInRange helpers.
src/FileProviders/Embedded/src/Manifest/EmbeddedFilesManifest.cs	Uses SearchValues<char> for invalid path char search when NET8_0_OR_GREATER.
src/FileProviders/Embedded/src/EmbeddedFileProvider.cs	Uses SearchValues<char> for invalid path char search when NET8_0_OR_GREATER.
src/Components/Web/src/Forms/Mapping/FormMappingError.cs	Simplifies separator search using LastIndexOfAny('.', '[').
src/Components/Web/src/Forms/FieldIdGenerator.cs	Uses ContainsAny(InvalidIdChars) for the fast-path check.