Update __wasi_sock_accept signature to match wasi_snapshot_preview1 (#1531)

The function was introduced to WASI about half a year ago after it already
existed in WAMR.

It caused problems with compiling `wasi_socket_ext.c` with the wasi-sdk
that already had this hostcall exported (wasi-sdk >= 15).

The approach we take is the following:
- we update WASI interface to be compatible with the wasi_snapshot_preview1
- compilation with `wasi_socket_ext.c` supports both wasi_sdk >= 15 and wasi_sdk < 15
  (although we intend to drop support for < 15 at one point of time)
- we override `accept()` from wasi-libc - we do that because `accept()` in `wasi-libc`
  doesn't support returning address (as it doesn't have `getpeername()` implemented),
  so `wasi_socket_ext.c` offers more functionality right now

Resolves #1167 and #1528.

[1] https://github.com/WebAssembly/WASI/blob/main/phases/snapshot/witx/wasi_snapshot_preview1.witx

core/iwasm/libraries/libc-wasi/sandboxed-system-primitives/src/posix.c

@@ -2905,7 +2905,7 @@ wasi_ssp_sock_accept(
 #if !defined(WASMTIME_SSP_STATIC_CURFDS)
     struct fd_table *curfds,
 #endif
-    __wasi_fd_t fd, __wasi_fd_t *fd_new)
+    __wasi_fd_t fd, __wasi_fdflags_t flags, __wasi_fd_t *fd_new)
 {
     __wasi_filetype_t wasi_type;
     __wasi_rights_t max_base, max_inheriting;