RFR: JDK-8310913 Move ReferencedKeyMap to jdk.internal so it may be shared [v10]

[ExE Boss]

On Mon, 5 Feb 2024 16:59:51 GMT, Jim Laskey <jlaskey at openjdk.org> wrote:

>> ok, `intern(e) == e` is sufficient.
>
> Created https://bugs.openjdk.org/browse/JDK-8325255

While `intern(e) == e` is (mostly) sufficient, it will return a false positive when `add(e)` is called and `e` is already present in the map, the correctest implementation would be some internal API in `ReferencedKeyMap` for implementing `ReferencedKeySet::add`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14684#discussion_r1485634936