Init inlining & panic=unwind reinitialization

[guybedford]

This is a rework of #962, that is based to wasm-bindgen/wasm-bindgen#5083 supporting multiple start functions for wasm bindgen.

With this, we are able to fully inline our init system, and then support the Rust-based panic hook for both panic=abort and panic=unwind, based on JS initState object as in #962.

Then, under panic=unwind it uses a reduced wrapper to use the native reinitalization support in wasm bindgen instead of needing to do this ourselves in the wrapper.

In the process, aborts are now fully handled for unwind, based on abort reinitialization, with the tests updated accordingly.

Non-panic abort detection for still requires further upstream work in wasm bindgen before we can support this fully for panic=abort, with the remaining commented test covering this.

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

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✅ 2 untouched benchmarks

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_{Comparing init (8f8324b) with main (bd2dfa5)}