perf(userland): replace sys_yield with sleep for WAY better idle efficiency

src/userland/libc/posix_io.c

@@ -158,7 +158,7 @@ static int _b_pipe_read(fd_handle_t *h, void *buf, size_t count) {
                 }
                 break;
             }
-            sys_yield();
+            sleep(1);
             continue;
         }
 
@@ -193,7 +193,7 @@ static int _b_pipe_write(fd_handle_t *h, const void *buf, size_t count) {
                 }
                 break;
             }
-            sys_yield();
+            sleep(1);
             continue;
         }
 

src/userland/libc/posix_process.c

@@ -3,6 +3,7 @@
 
 #include "errno.h"
 #include "stdio.h"
+#include "stdlib.h"
 #include "string.h"
 #include "sys/types.h"
 #include "sys/wait.h"
@@ -219,6 +220,6 @@ __attribute__((weak)) pid_t waitpid(pid_t pid, int *status, int options) {
             errno = ECHILD;
             return -1;
         }
-        sys_yield();
+        sleep(1);
     }
 }