test: internal: stream_processor: Plug a SEGV for macOS (fluent#10404)

Without TLS initialization, we got the following error on macOS:

```
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
    frame #0: 0x0000000100b0defc flb-it-stream_processor`_mk_event_timeout_create(ctx=0x0000000000000000, sec=0, nsec=500000000, data=0x0000600001608460) at mk_event_kqueue.c:222:23
   219         EV_SET(&ke, fd, EVFILT_TIMER, EV_ADD, 0, (sec * 1000) + (nsec / 1000000) , event);
   220     #endif
   221
-> 222         ret = kevent(ctx->kfd, &ke, 1, NULL, 0, NULL);
   223         if (ret < 0) {
   224             close(fd);
   225             mk_libc_error("kevent");
Target 0: (flb-it-stream_processor) stopped.
```

This can be plugged by TLS initialization for eventloop.

Signed-off-by: Hiroshi Hatake <[email protected]>

Author: cosmo0920

tests/internal/stream_processor.c

@@ -815,6 +815,7 @@ static void test_conv_from_str_to_num()
 
     config = flb_config_init();
     config->evl = mk_event_loop_create(256);
+    flb_engine_evl_init();
     flb_engine_evl_set(config->evl);
 
     ret = flb_storage_create(config);