LibJS/Bytecode: Make StringTableIndex be a 32-bit index

This makes a bunch of instructions smaller.

Userland/Libraries/LibJS/Bytecode/StringTable.h

@@ -12,7 +12,7 @@
 
 namespace JS::Bytecode {
 
-AK_TYPEDEF_DISTINCT_NUMERIC_GENERAL(size_t, StringTableIndex, Comparison);
+AK_TYPEDEF_DISTINCT_NUMERIC_GENERAL(u32, StringTableIndex, Comparison);
 
 class StringTable {
     AK_MAKE_NONMOVABLE(StringTable);

Userland/Libraries/LibJS/Forward.h

@@ -315,7 +315,7 @@ class MarkedVector;
 
 namespace Bytecode {
 class BasicBlock;
-enum class Builtin;
+enum class Builtin : u8;
 class Executable;
 class Generator;
 class Instruction;