LibJS: Rename OrdinaryFunctionObject to ECMAScriptFunctionObject

The old name is the result of the perhaps somewhat confusingly named
abstract operation OrdinaryFunctionCreate(), which creates an "ordinary
object" (https://tc39.es/ecma262/#ordinary-object) in contrast to an
"exotic object" (https://tc39.es/ecma262/#exotic-object).

However, the term "Ordinary Function" is not used anywhere in the spec,
instead the created object is referred to as an "ECMAScript Function
Object" (https://tc39.es/ecma262/#sec-ecmascript-function-objects), so
let's call it that.

The "ordinary" vs. "exotic" distinction is important because there are
also "Built-in Function Objects", which can be either implemented as
ordinary ECMAScript function objects, or as exotic objects (our
NativeFunction).

More work needs to be done to move a lot of infrastructure to
ECMAScriptFunctionObject in order to make FunctionObject nothing more
than an interface for objects that implement [[Call]] and optionally
[[Construct]].

Userland/Libraries/LibJS/Tests/builtins/Symbol/Symbol.keyFor.js

@@ -15,7 +15,7 @@ test("bad argument values", () => {
         [{}, "[object Object]"],
         [true, "true"],
         ["foobar", "foobar"],
-        [function () {}, "[object OrdinaryFunctionObject]"], // FIXME: Better function stringification
+        [function () {}, "[object ECMAScriptFunctionObject]"], // FIXME: Better function stringification
     ].forEach(testCase => {
         expect(() => {
             Symbol.keyFor(testCase[0]);