wasm-node: On panic, load a separate Wasm source map and resolve the backtrace

[tomaka]

After rust-lang/rust#34651 it should be possible to generate DWARF debug info for the Wasm node.
(see also https://github.com/WebAssembly/meetings/blob/main/debugging/2020/debugging-09-17.md#notes)

Assuming generating DWARF debug info works, we could tweak the JS code of the Worker to load these debug info when smoldot panics and resolve the panic backtrace.

This is all rather difficult and theoretical, so this is a long term issue.