fix(core): normalize Windows source map paths - #2102

Motivation

Windows builds with devtool: 'source-map' can emit a source such as C:\project\src/file.js while the module graph uses C:\project\src\file.js. The absolute-path branch kept the mixed separators, so the source did not match its module and its bundled size stayed at zero.

In a real Rspack 2.2.8 reproduction, the default source-map configuration reports 0 bytes before this fix and 3578 bytes after it, with identical emitted JavaScript. An explicitly normalized source-map template reports 3578 bytes both before and after.

Changes

• Route absolute sources through the existing cached resolver before collecting code and checking skipSources.
• On Windows, normalize full drive paths and ordinary UNC paths. Preserve POSIX/root-relative paths and device namespaces, and retain the existing URI and relative-source resolution.
• Add eight unit cases covering path forms, loader/query extraction, caching and cross-asset deduplication, plus a real compilation case that verifies two modules receive their own generated code and matching sizes.

Validation on Windows with Node 22.23.2:

• Full workspace build passed.
• pnpm --filter @rsdoctor/core run test: 378 passed, 1 existing Windows skip in the concurrent atomic-write suite.
• Focused source-map unit tests: 24 passed; six new cases fail on the baseline.
• rs test run sourcemap in e2e: 4 passed, 0 skipped; the new default-source-map case fails on the baseline with parsedSize = 0.
• rs check --type-check: lint, type and formatting checks passed.
• The public-API reproduction now reports 3578 bytes for both default and explicit raw source-map templates; generated JavaScript and map fields other than source names remain identical to the original control builds.