Remove dead code: extent_commit_wrapper, large_salloc, tcache_gc_dalloc event waits

These functions had zero callers anywhere in the codebase:
- extent_commit_wrapper: wrapper never called, _impl used directly
- large_salloc: trivial wrapper never called
- tcache_gc_dalloc_new_event_wait: no header declaration, no callers
- tcache_gc_dalloc_postponed_event_wait: no header declaration, no callers

src/large.c

@@ -276,11 +276,6 @@ large_dalloc(tsdn_t *tsdn, edata_t *edata) {
 	arena_decay_tick(tsdn, arena);
 }
 
-size_t
-large_salloc(tsdn_t *tsdn, const edata_t *edata) {
-	return edata_usize_get(edata);
-}
-
 void
 large_prof_info_get(
     tsd_t *tsd, edata_t *edata, prof_info_t *prof_info, bool reset_recent) {