Implement GC (Garbage Collection) feature for interpreter, AOT and LLVM-JIT (#3125)

Implement the GC (Garbage Collection) feature for interpreter mode,
AOT mode and LLVM-JIT mode, and support most features of the latest
spec proposal, and also enable the stringref feature.

Use `cmake -DWAMR_BUILD_GC=1/0` to enable/disable the feature,
and `wamrc --enable-gc` to generate the AOT file with GC supported.

And update the AOT file version from 2 to 3 since there are many AOT
ABI breaks, including the changes of AOT file format, the changes of
AOT module/memory instance layouts, the AOT runtime APIs for the
AOT code to invoke and so on.

core/iwasm/include/wasm_export.h

@@ -161,6 +161,9 @@ typedef struct RuntimeInitArgs {
     /* Fast JIT code cache size */
     uint32_t fast_jit_code_cache_size;
 
+    /* Default GC heap size */
+    uint32_t gc_heap_size;
+
     /* Default running mode of the runtime */
     RunningMode running_mode;