Update to cranelift 0.20.0.

The biggest change is the split from FunctionIndex to
DefinedFuncIndex to FuncIndex. Take better advantage of this by
converting several Vecs to PrimaryMaps.

Also, table_addr can now handle indices of the table index type,
so we don't need to explicitly uextend them anymore.

lib/execute/Cargo.toml

@@ -8,8 +8,9 @@ repository = "https://github.com/CraneStation/wasmtime"
 license = "Apache-2.0 WITH LLVM-exception"
 
 [dependencies]
-cranelift-codegen = "0.18.1"
-cranelift-wasm = "0.18.1"
+cranelift-codegen = "0.20.0"
+cranelift-entity = "0.20.1"
+cranelift-wasm = "0.20.1"
 region = "0.3.0"
 wasmtime-environ = { path = "../environ" }
 memmap = "0.6.2"