Userland: static vs non-static constexpr variables

Problem:
- `static` variables consume memory and sometimes are less
  optimizable.
- `static const` variables can be `constexpr`, usually.
- `static` function-local variables require an initialization check
  every time the function is run.

Solution:
- If a global `static` variable is only used in a single function then
  move it into the function and make it non-`static` and `constexpr`.
- Make all global `static` variables `constexpr` instead of `const`.
- Change function-local `static const[expr]` variables to be just
  `constexpr`.

Userland/Libraries/LibX86/Instruction.h

@@ -28,9 +28,9 @@ protected:
 
 template<typename T>
 struct TypeTrivia {
-    static const size_t bits = sizeof(T) * 8;
-    static const T sign_bit = 1 << (bits - 1);
-    static const T mask = MakeUnsigned<T>(-1);
+    static constexpr size_t bits = sizeof(T) * 8;
+    static constexpr T sign_bit = 1 << (bits - 1);
+    static constexpr T mask = MakeUnsigned<T>(-1);
 };
 
 template<typename T, typename U>
@@ -159,9 +159,9 @@ enum InstructionFormat {
     OP_NEAR_imm,
 };
 
-static const unsigned CurrentAddressSize = 0xB33FBABE;
-
 struct InstructionDescriptor {
+    static constexpr unsigned CurrentAddressSize = 0xB33FBABE;
+
     InstructionHandler handler { nullptr };
     bool opcode_has_register_index { false };
     const char* mnemonic { nullptr };