Improve logging performance and make log priorities thread-safe

Fixes https://github.com/libsdl-org/SDL/issues/9679

test/testver.c

@@ -19,9 +19,6 @@
 
 int main(int argc, char *argv[])
 {
-    /* Enable standard application logging */
-    SDL_SetLogPriority(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_INFO);
-
     if (argc > 1) {
         SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "USAGE: %s", argv[0]);
         return 1;