Fix clang-tidy performance-enum-size warnings in headers

src/script_opt/CPP/AttrExprType.h

@@ -4,9 +4,11 @@
 
 #pragma once
 
+#include <cstdint>
+
 namespace zeek::detail {
 
-enum AttrExprType {
+enum AttrExprType : uint8_t {
     AE_NONE,   // attribute doesn't have an expression
     AE_CONST,  // easy expression - a constant (ConstExpr)
     AE_NAME,   // easy - a global (NameExpr)

src/script_opt/CPP/Exprs.h

@@ -16,7 +16,10 @@
 // values, the end goal is to have the value in (1) native form, (2) instead
 // in ValPtr form, or (3) whichever is more convenient to generate (sometimes
 // used when the caller knows that the value is non-native).
-enum GenType {
+
+#include <cstdint>
+
+enum GenType : uint8_t {
     GEN_NATIVE,
     GEN_VAL_PTR,
     GEN_DONT_CARE,