Rework casting in raw_hash_set's IsFull().

Instead of casting an int to the enum type where the int does not have an associated enum value, cast the enum to its underlying type. This should be no functional change but make some linters happier.

PiperOrigin-RevId: 611172311
Change-Id: I9ae10f8fa2029014236f60a90ee2ab2273c66fa5

Author: grebe

absl/container/internal/raw_hash_set.h

@@ -571,7 +571,9 @@ inline h2_t H2(size_t hash) { return hash & 0x7F; }
 
 // Helpers for checking the state of a control byte.
 inline bool IsEmpty(ctrl_t c) { return c == ctrl_t::kEmpty; }
-inline bool IsFull(ctrl_t c) { return c >= static_cast<ctrl_t>(0); }
+inline bool IsFull(ctrl_t c) {
+  return static_cast<std::underlying_type_t<ctrl_t>>(c) >= 0;
+}
 inline bool IsDeleted(ctrl_t c) { return c == ctrl_t::kDeleted; }
 inline bool IsEmptyOrDeleted(ctrl_t c) { return c < ctrl_t::kSentinel; }