fix: Node shims for 'javascript/esm' files

[Timeless0911]

Summary

__filename and __dirname shims should work in 'javascript/esm' files.

Related Links

web-infra-dev/rspack#11840

Checklist

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

[Copilot]

Pull Request Overview

This PR fixes Node.js shims (__filename and __dirname) to work properly in 'javascript/esm' files by adding support for .mjs files and ensuring the RslibPlugin forces Node shims when these variables are enabled in ESM shim configuration.

• Added test coverage for Node.js shims in .mjs files
• Updated RslibPlugin configuration to force Node shims when ESM shims are enabled
• Enhanced test configuration to include a new ESM bundle with .mjs entry point

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/integration/shims/index.test.ts	Added test case for Node.js shims in .mjs files and updated existing test references
tests/integration/shims/esm/src/node.mjs	New test file demonstrating __dirname and __filename usage in ESM module
tests/integration/shims/esm/rslibShimsDisabled.config.ts	Updated to include all lib configurations in shims disabled tests
tests/integration/shims/esm/rslib.config.ts	Added new ESM bundle configuration for .mjs file testing and reformatted existing configs
packages/core/src/config.ts	Added forceNodeShims option to RslibPlugin based on enabled ESM shims

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