Implement module instance context APIs (#2436)

Introduce module instance context APIs which can set one or more contexts created
by the embedder for a wasm module instance:
```C
    wasm_runtime_create_context_key
    wasm_runtime_destroy_context_key
    wasm_runtime_set_context
    wasm_runtime_set_context_spread
    wasm_runtime_get_context
```

And make libc-wasi use it and set wasi context as the first context bound to the wasm
module instance.

Also add samples.

Refer to https://github.com/bytecodealliance/wasm-micro-runtime/issues/2460.

core/iwasm/common/wasm_native.h

@@ -68,6 +68,36 @@ bool
 wasm_native_unregister_natives(const char *module_name,
                                NativeSymbol *native_symbols);
 
+#if WASM_ENABLE_MODULE_INST_CONTEXT != 0
+struct WASMModuleInstanceCommon;
+
+void *
+wasm_native_create_context_key(
+    void (*dtor)(struct WASMModuleInstanceCommon *inst, void *ctx));
+
+void
+wasm_native_destroy_context_key(void *key);
+
+void
+wasm_native_set_context(struct WASMModuleInstanceCommon *inst, void *key,
+                        void *ctx);
+void
+wasm_native_set_context_spread(struct WASMModuleInstanceCommon *inst, void *key,
+                               void *ctx);
+void *
+wasm_native_get_context(struct WASMModuleInstanceCommon *inst, void *key);
+
+void
+wasm_native_call_context_dtors(struct WASMModuleInstanceCommon *inst);
+
+void
+wasm_native_inherit_contexts(struct WASMModuleInstanceCommon *child,
+                             struct WASMModuleInstanceCommon *parent);
+#else /* WASM_ENABLE_MODULE_INST_CONTEXT */
+#define wasm_native_call_context_dtors(inst) (void)(inst)
+#define wasm_native_inherit_contexts(child, parent) (void)(parent)
+#endif /* WASM_ENABLE_MODULE_INST_CONTEXT */
+
 bool
 wasm_native_init();