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/Runtime/FunctionObject.h

@@ -11,7 +11,6 @@
 
 namespace JS {
 
-// 10.2 ECMAScript Function Objects, https://tc39.es/ecma262/#sec-ecmascript-function-objects
 class FunctionObject : public Object {
     JS_OBJECT(Function, Object);