Counterpart to language/expressions/object/prop-def-invalid-async-prefix.js.

https://github.com/tc39/ecma262/pull/1433

Spec PR: tc39/ecma262#1372

Remove invalid private name tests and guard against missing bindings

Inner classes have access to outer private names.

Fixes #2039

This is based on UTS35 in the new spec.

According to sec-identifiers-static-semantics-assignmenttargettype,
`AssignmentTargetType` of `arguments` and `eval` in non-strict mode code is
`simple`.
sec-update-expressions-static-semantics-early-errors mandates early errors for
`UpdateExpression` if `AssignmentTargetType` is `invalid` or `strict`.

Add test for case of -kn-true
Verify no -kn-true nor -kn-false in the returned locale.
Change expectation per https://github.com/tc39/ecma402/pull/302

See https://tc39.github.io/proposal-intl-locale/#sec-canonicalizelocalelist

This is due to the fact we now only accept Unicode Locale Identifier in
UTS 35.

Previously, the early error prohibiting duplicate entries in
UniqueFormalParameters was only tested in terms of async functions. In
one case, this was misattributed to UniqeFormalParameters and only
enforced for strict mode code.

Extend coverage to the other function-creating productions which include
UniqueFormalParameters (i.e. method definitions and non-async arrow
functions), and update the existing tests to more accurately describe
the source of the error.