fix(wasip2): export _initialize

[rvolosatovs]

Closes #4488
Refs #4482

Turns out _initialize was not exported by wasip2 components and so init() was never called in reactors. This PR fixes that, by initializing the heap and calling all initializers, just like run() would normally do

Note: wasm-tools 1.217 or later are required for init() to work in reactors (since _initialize is ignored in earlier versions, see bytecodealliance/wasm-tools#1747)

Thanks @alexcrichton for assisting in debugging this in https://bytecodealliance.zulipchat.com/#narrow/stream/217126-wasmtime/topic/calling.20.60_initialize.60

[lxfontes]

ran same scenario as in #4482

Before

varHolder: {str:top ptr:0x15b30 mapStr:map[] mapPtr:map[]}
ptrHolder: &{str:top ptr:0x15b40 mapStr:map[] mapPtr:map[]}
callHolder: {str:top ptr:0x15df0 mapStr:map[a:b] mapPtr:map[c:0x16140]}

With this PR

varHolder: {str:top ptr:0x15b38 mapStr:map[a:b] mapPtr:map[c:0x15b40]}
ptrHolder: &{str:top ptr:0x15b48 mapStr:map[a:b] mapPtr:map[c:0x15b50]}
callHolder: {str:top ptr:0x164c0 mapStr:map[a:b] mapPtr:map[c:0x16720]}

🎉

[aykevl]

With this change, if wasi:cli/run@0.2.0#run is called, the package initializers will be called twice. I don't think that's the intention?

[rvolosatovs]

With this change, if wasi:cli/run@0.2.0#run is called, the package initializers will be called twice. I don't think that's the intention?

how about 03d535d ?

[dgryski]

/cc @ydnar

[rvolosatovs]

Looking at tests, it does not look like _initialize is actually called for run implementations?
Perhaps we need to call _initialize from within run and guard by sync.Once or such?

[rvolosatovs]

Reworked the PR a bit - initialization is now done always, but guarded by sync.OnceValue - since the spec is not completely clear on the semantics here, this ensures that initialization is done for both reactors and command components.

For reactors, runtime must always call _initialize and for commands it may not

[aykevl]

Looking at tests, it does not look like _initialize is actually called for run implementations?

That's not how I understand the wasip2 spec, my understanding is that _initialize needs to be called first in all cases but that it wasn't always done previously.

@ydnar?

[ydnar]

What version of wasm-tools is used to create the component? It needs at least v1.217.0: bytecodealliance/wasm-tools@v1.216.0...v1.217.0

The relevant commit is: bytecodealliance/wasm-tools@108c37d

[ydnar]

Once #3165 lands, the wasi:cli/command#run export should be wired up to call main.main and do nothing else.