feat: support displaying the total size diff

[chenjiahan]

Summary

Add support for displaying the total size diff:

File (web)                             Size                   Gzip
dist/static/css/index.54800c1b.css     0.34 kB (+0.34 kB)     0.25 kB (+0.25 kB)
dist/index.html                        0.37 kB (+0.12 kB)     0.25 kB (+0.05 kB)
dist/static/js/index.f31cb805.js       1.3 kB (+1.3 kB)       0.76 kB (+0.74 kB)
dist/static/js/lib-react.6cc087e6.js   189.8 kB (+189.8 kB)   59.9 kB (+59.9 kB)

                              Total:   191.8 kB (+191.6 kB)   61.2 kB (+61.0 kB)

Checklist

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

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[Copilot]

Pull request overview

This PR adds support for displaying size difference information in the total row of the file size output, complementing the existing per-file diff display. The implementation tracks total sizes across builds and shows diffs for both regular and gzipped sizes when diff mode is enabled.

Key Changes

• Introduced SizeSnapshot type to encapsulate file sizes along with aggregate total and gzip sizes
• Extended diff display to show total size changes (e.g., Total: 191.8 kB (+191.6 kB))
• Added gzip total diff display in detail mode for comprehensive size tracking

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[andrzej-erli]

Hi, I'd like to know, whether this feature supports multiple configurations? Docs https://rsbuild.rs/config/performance/print-file-size mention only one file <root>/node_modules/.cache/rsbuild/file-sizes.json but I run multiple configurations using the same node_modules, eg. rsbuild build -c scripts/config/rsbuild.config.mts rsbuild build -c server/rsbuild.config.mts etc.

[chenjiahan]

This feature works across multiple environments, but it doesn't support multiple Rsbuild configurations yet. I can add support for that.