Disconnects Store state fields from Compiler (#1761)

*  Moves CodeMemory, VMInterrupts and SignatureRegistry from Compiler
*  CompiledModule holds CodeMemory and GdbJitImageRegistration
*  Store keeps track of its JIT code
*  Makes "jit_int.rs" stuff Send+Sync
*  Adds the threads example.

crates/test-programs/tests/wasm_tests/runtime.rs

@@ -53,7 +53,7 @@ pub fn instantiate(
 
     snapshot1.add_to_linker(&mut linker)?;
 
-    let module = Module::new(&store, &data).context("failed to create wasm module")?;
+    let module = Module::new(store.engine(), &data).context("failed to create wasm module")?;
 
     linker
         .module("", &module)