Use context fields instead of thread_local to store error.

[mayuki]

This PR changes to use context fields instead of thread_local to store error.
On devices such as Android, TLS may not be available, so we will reduce the use of TLS.

[Copilot]

Pull Request Overview

This PR removes the use of thread_local storage for error messages and instead uses context fields to store error data, improving compatibility on devices without TLS.

• Updated native method signatures and error handling to pass context fields.
• Adjusted test cases and helper methods to use the new API.
• Modified native bindings and build scripts to align with the updated error handling approach.

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/YetAnotherHttpHandler.Test/NativeMethodsTest.cs	Updated test to acquire and release runtime handles and use context-based error retrieval.
src/YetAnotherHttpHandler/ThrowHelper.cs	Changed the signature of ThrowIfFailed to take context pointers and updated error retrieval accordingly.
src/YetAnotherHttpHandler/RequestContext.cs	Updated request completion to call the revised ThrowIfFailed with context parameters.
src/YetAnotherHttpHandler/NativeMethods.g.cs src/YetAnotherHttpHandler/NativeMethods.Uwp.g.cs	Updated P/Invoke signatures for yaha_get_last_error to accept context fields instead of using thread_local.
src/YetAnotherHttpHandler/NativeHttpHandlerCore.cs	Updated multiple calls to ThrowIfFailed and error retrieval to pass context parameters.
native/yaha_native/src/context.rs	Changed runtime creation using Builder and added a last_error field in the request context.
native/yaha_native/src/binding.rs	Removed thread_local error handling and replaced it with context-based error management; adjusted various error-setting locations accordingly.
native/yaha_native/build.rs	Updated OS detection using environment variables for building Windows resources.