This introduces a Wasmtime configuration file to get some CLI options out of the code for easier manipulation. It also allows for easier tweaking after the Makefile is generated.
As well, cut back on the flexibility of specifying HOSTRUNNER for simpler code. The flexibility was never used and so it didn't make sense to keep it around.
This commit updates CI and configuration from wasi-sdk-25 to wasi-sdk-29
which was released recently. This notably includes stubs for pthreads
which all return errors, so some adjustment in logic is necessary to
retain knowledge that WASI cannot yet spawn threads for example.
This additionally increases the wasm stack allowance to 32MiB from 16MiB
to accomodate the `test_recursive_pickle` test in the
`test_functools.py` file. It looks like the Clang/LLVM update that
happened in wasi-sdk-29 relative to wasi-sdk-25 is likely the cause of
this where presumably functions have more locals than before and/or a
slightly adjusted stack space requirement which overflows the stack.
