canary

update Wasmtime and WASIp3 WITs, etc. (#211)

* support multiple `-w` options; update to latest Wasmtime

This also updates the WASIp3 examples and WIT files to use the latest RC.

* add `--full-names` option and refactor public API

`clippy` finally convinced me there were too many arguments to the
`componentize` function, so now we have methods on structs with named fields
instead.

Also, print all known worlds and WIT paths if the specified world can't be
found.

* fix python.rs build

* add new WIT files

* pin mypy version used for tests

* bump Wasmtime version in test.yaml