wasmtime: Extract cranelift/lightbeam compilers to separate crates (#2117)

This commit extracts the two implementations of `Compiler` into two
separate crates, `wasmtime-cranelfit` and `wasmtime-lightbeam`. The
`wasmtime-jit` crate then depends on these two and instantiates them
appropriately. The goal here is to start reducing the weight of the
`wasmtime-environ` crate, which currently serves as a common set of
types between all `wasmtime-*` crates. Long-term I'd like to remove the
dependency on Cranelift from `wasmtime-environ`, but that's going to
take a lot more work.

In the meantime I figure it's a good way to get started by separating
out the lightbeam/cranelift function compilers from the
`wasmtime-environ` crate. We can continue to iterate on moving things
out in the future, too.

scripts/publish.rs

@@ -56,6 +56,8 @@ const CRATES_TO_PUBLISH: &[&str] = &[
     "wasmtime-debug",
     "wasmtime-profiling",
     "wasmtime-obj",
+    "wasmtime-cranelift",
+    "wasmtime-lightbeam",
     "wasmtime-jit",
     "wasmtime-cache",
     "wasmtime",
@@ -298,7 +300,7 @@ fn verify(crates: &[Crate]) {
             .arg("--manifest-path")
             .arg(&krate.manifest)
             .env("CARGO_TARGET_DIR", "./target");
-        if krate.name == "lightbeam" || krate.name == "witx" {
+        if krate.name.contains("lightbeam") || krate.name == "witx" {
             cmd.arg("--no-verify");
         }
         let status = cmd.status().unwrap();