Tracking issue for shared memory

This issue tracks anything incomplete with the effort to add shared memories started in #4187:

- [x] https://github.com/bytecodealliance/wasm-tools/pull/624
- [x] https://github.com/bytecodealliance/wasmtime/pull/4266
- [x] improve tests (@alexcrichton had a [comment](https://github.com/bytecodealliance/wasmtime/pull/4187#discussion_r891697133) about trying to stress things by doing more in Wasm)
- [ ] add a `SharedMemoryType` to the `wasmtime` external API (@alexcrichton wanted this to disambiguate entirely between memories and shared memories
- [x] enable shared memory in the C API (#7940)
- [ ] #4244
- [ ] #4240
- [ ] #4203
- [x] #4267
- [ ] #4268
- [ ] Growth/creation of a shared memory is not subject to resource limiters
- [ ] Shared memories are disabled by default in Wasmtime
- [ ] Pulley's reconcilation with shared memories may or may not have holes (unsure)
- [ ] Behavior of wait/notify aren't customizable #12809