Part of the ongoing quest to support JSPI. The JSPI spec removed its dependence on
JS type reflection, and now the plan is for runtimes to ship JSPI while keeping
type reflection in stage 3. So we need an alternative way to count the number of
parameters of a function. It is possible to count them by repeatedly trying to
instantiate a webassembly module with the function as an import of a different type
signature. But this is pretty inefficient.

Since WebAssembly gc is now stage 4, there is a new option. WebAssembly gc added the
`ref.test` instruction which can ask if a funcref has a given type. It's a bit difficult
to apply because even our usual assembler the wasm binary toolkit doesn't support this
instruction yet. But all JS engines that support JSPI support it. We just have to do some
manual work to produce the binary.

This code also has to be written carefully to interact properly with memory snapshots.
Importantly, no JS initialization code can be called from the C initialization code.
For this reason, we make a C function pointer to fill from JS and fill it in a preRun
function.

…128628)

Replaces the trampoline mechanism in Emscripten with an implementation that uses a
recently added feature of wasm-gc instead of JS type reflection, when that feature is
available.

…poline

We need to divide the entire memory address by 4, not just the base address.

…#128782)

Modifies the memory calculation to divide the entire memory address by 4, not just the base address.

As of iOS 18.3.1, enabling wasm-gc is making the interpreter fail to load.
Downstream pyodide issue: pyodide/pyodide#5428.

macOS Safari 18.3 does not surface the issue.

Confirmed on device that disabling this restores interpreter function.

As of iOS 18.3.1, enabling wasm-gc breaks the interpreter. This disables the wasm-gc
trampoline on iOS.

Co-authored-by: Hood Chatham <roberthoodchatham@gmail.com>

…#130418)

As of iOS 18.3.1, enabling wasm-gc breaks the interpreter. This disables the wasm-gc
trampoline on iOS.

Co-authored-by: Hood Chatham <roberthoodchatham@gmail.com>