Change start WW id value in hybrid threading mode (#26660)

Linux TID/PID values have a max limit of 4,194,304. We should mimic that
and start WW id at 4,194,304/2.

Author: stephenduong1004

src/lib/libwasm_worker.js

@@ -65,10 +65,10 @@ addToLibrary({
 #if PTHREADS
   // When the build contains both pthreads and Wasm Workers, offset the
   // Wasm Worker ID space to avoid collisions with pthread TIDs (which start
-  // at 42). We use `1 << 30` since it's ~1/2 way through `pid_t` space,
+  // at 42). We use `1 << 21` since it's ~1/2 way through `pid_t` space,
   // essentially giving pthreads the first 1/2 of the range and wasm workers the
   // second half.
-  $_wasmWorkersID: {{{ 1 << 30 }}},
+  $_wasmWorkersID: {{{ 1 << 21 }}},
 #else
   $_wasmWorkersID: 1,
 #endif