[source debug] refine some code in source debugging (#856)

- move the wait_cond from exec_env to debug_instance, so the debug thread can be waken up by any threads
- process more general query message from debugger
- refine debug instance create/destroy mechanism
- avoid creating debug instance during module instantiating
- avoid blocking execution thread during creating debug instance
- update related documents

core/iwasm/interpreter/wasm_runtime.h

@@ -320,7 +320,8 @@ wasm_call_function(WASMExecEnv *exec_env, WASMFunctionInstance *function,
 bool
 wasm_create_exec_env_and_call_function(WASMModuleInstance *module_inst,
                                        WASMFunctionInstance *function,
-                                       unsigned argc, uint32 argv[]);
+                                       unsigned argc, uint32 argv[],
+                                       bool enable_debug);
 
 bool
 wasm_create_exec_env_singleton(WASMModuleInstance *module_inst);