examples: threads.rs; fixed eun typo -> run (bytecodealliance#2422)

Bump to 0.21.0 (bytecodealliance#2359)

Add metadata to peepmatic crates (bytecodealliance#2245)

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.

Wasmtime 0.17.0 and Cranelift 0.64.0. (bytecodealliance#1805)

Update release notes, wasmtime 0.16, cranelift 0.63.

Update the env var name in more places.

Update the env var name in more places.

Wasmtime 0.15.0 and Cranelift 0.62.0. (bytecodealliance#1398)