This separates `classPrivateMethods`'s dependency on
`classPrivateProperties`. It also starts a `PrivateName` at the hash
symbol, not the `Identifier`.
* Add support for class private methods
This commit adds parser support for the TC39 Stage 2 Private Methods
proposal.
This commit also changes "key" in ClassPrivateProperty from an
Identifier to a PrivateName, as well as disallowing #constructor as a
valid private field name.
* Add tests for string literal get/set/async
These should be treated as regular methods and not special get/set/async
behaviour.
* Add tests for class private methods
This also removes a test from the Test262 whitelist that failed before
the changes for private methods support and now passes.
* Modify class private prop tests for PrivateName
* Add class private prop tests for #constructor
* Fix existing ASI test case failure
