RFR: Split out ContinuationEntry and ContinuationWrapper [v2]

[Coleen Phillimore]

On Wed, 13 Apr 2022 14:53:24 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Tested locally.  Mach5 too lame to test this.
>
> Coleen Phillimore has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:
> 
>  - Moved ContinuationWrapper out of continuation.cpp
>  - Split ContinuationEntry out of Continuation

Going to redo this.

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PR: https://git.openjdk.java.net/loom/pull/143