The cmLinkImplItem class used to contain some additional members
to support the CMP0027 policy. Since the CMP0027 policy and those
associated members were removed, the cmLinkImplItem class has been
a plain wrapper around cmLinkItem with no additional members.
It is no longer needed and cmLinkItem can be used directly wherever
cmLinkImplItem was used previously.
Since commit 1e49880472 (cmGeneratorTarget: Avoid boolean trap in usage
requirement lookup, 2021-12-08, v3.23.0-rc1~245^2) we have clarified
the distinction between compile-only and link-only usage requirements.
Rename the `LinkInterfaceFor` enum to `UseTo` to clarify that its role
is to specify the purpose of usage requirements.