Implement async termination of blocking thread (#2516)

Send a signal whose handler is no-op to a blocking thread to wake up
the blocking syscall with either EINTR equivalent or partial success.

Unlike the approach taken in the `dev/interrupt_block_insn` branch (that is,
signal + longjmp similarly to `OS_ENABLE_HW_BOUND_CHECK`), this PR
does not use longjmp because:
* longjmp from signal handler doesn't work on nuttx
  refer to https://github.com/apache/nuttx/issues/10326
* the singal+longjmp approach may be too difficult for average programmers
  who might implement host functions to deal with

See also https://github.com/bytecodealliance/wasm-micro-runtime/issues/1910

core/shared/platform/freebsd/platform_internal.h

@@ -101,6 +101,12 @@ os_sigreturn();
 #endif /* end of BUILD_TARGET_X86_64/AMD_64/AARCH64/RISCV64 */
 #endif /* end of WASM_DISABLE_HW_BOUND_CHECK */
 
+#if WASM_DISABLE_WAKEUP_BLOCKING_OP != 0
+#define OS_ENABLE_WAKEUP_BLOCKING_OP
+#endif
+void
+os_set_signal_number_for_blocking_op(int signo);
+
 #ifdef __cplusplus
 }
 #endif