Bump version to 0.24.0

I used a specially modified version of the publish script to avoid
bumping the `witx` version.

Bump version to 0.23.0

I used a specially modified version of the publish script to avoid
bumping the `witx` version.

Bump smallvec dependency to 1.6.1

Merge pull request bytecodealliance#2557 from fitzgen/wasmtime-0.22.0

Wasmtime 0.22.0

Merge pull request bytecodealliance#2557 from fitzgen/wasmtime-0.22.0

Wasmtime 0.22.0

Bump to 0.21.0 (bytecodealliance#2359)

Add metadata to peepmatic crates (bytecodealliance#2245)

Increase into-func to accept 16 arguments (bytecodealliance#2170)

Wasmtime 0.19.0 and Cranelift 0.66.0 (bytecodealliance#2027)

This commit updates Wasmtime's version to 0.19.0, Cranelift's version to
0.66.0, and updates the release notes as well.

Wasmtime 0.18.0 and Cranelift 0.65.0.