This commit extends the options parsing system to tolerate the values
"11" and "2020" for the `esversion` linting option. It does not
introduce support for any features introduced by the new edition of the
language.

No call site for `propertyName` specifies an object value for the second
argument. The `optionalidentifier` function returns only string values
or undefined. These two invariants make the untested code paths
unreachable. Remove them both.

In so-called "object short notation," an IdentifierName is interpreted
as both a LiteralPropertyName and an IdentifierReference. The second is
a more restrictive goal than the first, so it is not necessary to apply
the LiteralPropertyName validation rules. Removing that validation logic
allows for an otherwise-unused parameter of the internal `propertyName`
function to be removed.

Extend consideration to include bindings created using
DestructuringBindingPattern.

Currently, the `setExported` method only makes the specified binding as
"used." This is unnecessary in this context because when `expression`
processes an IdentifierReference, it does the same. Remove the branch.

The situation described by this condition does not constitute
syntactically invalid code, so it should be reported with a warning.

Add an internal test so the coverage analysis tool recognizes that the
modified branch is verified.

Tolerate parsing errors regarding escape sequences in IdentifierNames as
these reflect a pre-existing deficiency which will require a dedicated
patch to correct.