feat: support lazy compilation in multi environments

[chenjiahan]

Summary

lazyCompilationMiddleware now supports lazy compilation when using multiple compiler.

Related Links

• refactor!: lazy compilation middleware supports multiCompiler and use config from compiler instance rspack#9828

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[Copilot]

Pull Request Overview

This PR updates lazyCompilationMiddleware to support lazy compilation for multi environments by removing the multi-compiler check.

• Remove the conditional logic that extracted the first compiler from a multi-compiler; the middleware now directly receives the entire compiler.
• Update the import statements accordingly.

Comments suppressed due to low confidence (2)

packages/core/src/server/devMiddlewares.ts:146

• The removal of the multi-compiler check means that lazyCompilationMiddleware now receives the full compiler instance. Please verify that the middleware is designed to handle multi-compiler setups without extracting a specific compiler and update the documentation if needed.

      rspack.experiments.lazyCompilationMiddleware(compiler) as RequestHandler,

packages/core/src/server/devMiddlewares.ts:4

• [nitpick] Since the isMultiCompiler function is no longer used, ensure that any related documentation or comments are updated to reflect that lazyCompilationMiddleware now directly accepts a multi-compiler instance.

import { pick } from '../helpers';