feat: router-based wasm bundle splitting

[jkelleyrtp]

Implements router-based wasm bundle splitting under an experimental flag --experimental-bundle-split.

The main implementation fits in a single file, which I think is necessary to keep the code maintainable given its inherent complexity.

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Takes a similar approach to https://github.com/jbms/wasm-split-prototype but does not manually encode wasm modules.

The original prototype is (imo) a bit too complex. The approach in this PR simply trims away portions of the modules and then uses the export/import map to connect them together. The only "indirect functions" we create are simply the functions at the #[wasm_split] boundaries.

I've tested everything against the harness, however I'd like to test it against the docsite which requires full dioxus-cli integration.

Everything is implemented (data section splitting, shared chunk extraction, lazy-loading, etc)

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Todo:

• wire up into the CLI
• wire up into the router (ideally with help from @ealmloff)
• Documentation
• Publish/reserve the wasm-split names on crates