internal/task: use asyncify on webassembly

This change implements a new "scheduler" for WebAssembly using binaryen's asyncify transform.
This is more reliable than the current "coroutines" transform, and works with non-Go code in the call stack.

runtime (js/wasm): handle scheduler nesting

If WASM calls into JS which calls back into WASM, it is possible for the scheduler to nest.
The event from the callback must be handled immediately, so the task cannot simply be deferred to the outer scheduler.
This creates a minimal scheduler loop which is used to handle such nesting.

Dockerfile

@@ -30,7 +30,7 @@ COPY --from=tinygo-base /tinygo/targets /tinygo/targets
 RUN cd /tinygo/ && \
     apt-get update && \
     apt-get install -y make clang-11 libllvm11 lld-11 && \
-    make wasi-libc
+    make wasi-libc binaryen
 
 # tinygo-avr stage installs the needed dependencies to compile TinyGo programs for AVR microcontrollers.
 FROM tinygo-base AS tinygo-avr