Enable anyhow feature by default in wasmtime (bytecodealliance#12422)

Relative to our other optional deps `anyhow` is pretty lightweight, so
enable the functionality by default.

Author: alexcrichton

crates/wasmtime/Cargo.toml

@@ -131,6 +131,7 @@ harness = false
 # for a particular embedding.
 [features]
 default = [
+  'anyhow',
   'async',
   'backtrace',
   'cache',