Add renaming of conflicting constructors and operations (#579)

* Add renaming of conflicting constructors and operations

* Rename conflicting to overloaded

* Fix newlines

* Use or_insert_with, add a comment to TypeToString

* Use more Rust-like names

* Use opt instead of nullable

* Use argument names instead of argument types if possible

* Drop new for overloaded constructots

* Remove extra newline

* Move WebIDL files from unavailable_overloaded_fn

* Move RTCDataChannel, RTCPeerConnection and Selection to unavailable_option_primitive

crates/web-sys/webidls/enabled/IDBKeyRange.webidl

@@ -20,7 +20,7 @@ interface IDBKeyRange {
   [Constant]
   readonly attribute boolean upperOpen;
   [Throws]
-  boolean includes(any key);
+  boolean _includes(any key);
 
 
   [NewObject, Throws]

crates/web-sys/webidls/unavailable_overloaded_fn/README.md

@@ -1,2 +0,0 @@
-These webidl files are unavailable because they have multiple functions with the same name and
-different arguments (overloaded functions), and web-sys does not support these.