Implement part of Berkeley Socket API for libc-wasi (#1036)

Refer to [Networking API design](https://github.com/WebAssembly/WASI/issues/370)
and [feat(socket): berkeley socket API v2](https://github.com/WebAssembly/WASI/pull/459):

- Support the socket API of synchronous mode, including `socket/bind/listen/accept/send/recv/close/shutdown`,
    the asynchronous mode isn't supported yet.
- Support adding `--addr-pool=<pool1,pool2,..>` argument for command line to identify the valid ip address range
- Add socket-api sample and update the document

core/iwasm/include/wasm_export.h

@@ -348,6 +348,10 @@ wasm_runtime_set_wasi_args(wasm_module_t module,
                            const char *env[], uint32_t env_count,
                            char *argv[], int argc);
 
+WASM_RUNTIME_API_EXTERN void
+wasm_runtime_set_wasi_addr_pool(wasm_module_t module, const char *addr_pool[],
+                                uint32_t addr_pool_size);
+
 /**
  * Instantiate a WASM module.
  *