Move prefetch_heap_block() from find() into find_large() (matching `find_or_prepare_insert_large()`).

In `raw_hash_set::find()`, calling `prefetch_heap_block()` before `find_large()` duplicates the `control()` load and `prefetcht2` instruction at every call site where `find()` is inlined but `find_large()` is not.

PiperOrigin-RevId: 1004962020

absl/container/internal/raw_hash_set.h

diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index e717125..1c1d709 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -3477,7 +3477,6 @@
   iterator find(const key_arg<K>& key) ABSL_ATTRIBUTE_LIFETIME_BOUND {
     AssertOnFind(key);
     if (is_small()) return find_small(key);
-    prefetch_heap_block();
     return find_large<FindLargeKey<key_arg<K>>>(key);
   }
 
@@ -3643,6 +3642,7 @@
   template <class K>
   iterator find_large(absl::type_identity_t<K> key) {
     static_assert(std::is_same_v<K, FindLargeKey<K>>);
+    prefetch_heap_block();
     const size_t hash = hash_of(key);
     const size_t cap = common().capacity();
     ABSL_ASSUME(cap > kMaxSmallCapacity);