LibJS: Bring Reference records a bit closer to the ECMAScript spec

Our Reference class now has the same fields as the spec:

- Base (a non-nullish value, an environment record, or `unresolvable`)
- Referenced Name (the name of the binding)
- Strict (whether the reference originated in strict mode code)
- ThisValue (if non-empty, the reference represents a `super` keyword)

The main difference from before is that we now resolve the environment
record that a reference interacts with. Previously we simply resolved
to either "local variable" or "global variable".

The associated abstract operations are still largely non-conforming,
since we don't yet implement proper variable bindings. But this patch
should at least fix a handful of test262 cases. :^)

There's one minor regression: some TypeError message strings get
a little worse due to doing a RequireObjectCoercible earlier in the
evaluation of MemberExpression.

Userland/Libraries/LibJS/Tests/strict-mode-errors.js

@@ -18,12 +18,9 @@ test("basic functionality", () => {
     [null, undefined].forEach(primitive => {
         expect(() => {
             primitive.foo = "bar";
-        }).toThrowWithMessage(TypeError, `Cannot set property 'foo' of ${primitive}`);
+        }).toThrowWithMessage(TypeError, `${primitive} cannot be converted to an object`);
         expect(() => {
             primitive[Symbol.hasInstance] = 123;
-        }).toThrowWithMessage(
-            TypeError,
-            `Cannot set property 'Symbol(Symbol.hasInstance)' of ${primitive}`
-        );
+        }).toThrowWithMessage(TypeError, `${primitive} cannot be converted to an object`);
     });
 });