RFR: Split out ContinuationEntry and ContinuationWrapper classes

[Ron Pressler]

On Thu, 14 Apr 2022 01:01:17 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

> Moved ContinuationEntry and ContinuationWrapper to their own files.
> There's a bit of inconsistency because 3 ContinuationEntry functions are in ContinuationHelper_cpu.inline.hpp - maybe we should have continuationEntry_cpu.inline.hpp files for just the three.
> I'd like to change the name ContinuationEntry to ContinuationAnchor or ContinuationFrameAnchor but want to study how that would look a bit more first.
> Tested with other platforms and testing with loom-tier1 as sanity.

Because the JFR event fields are only used in freeze and thaw (and only for perf debugging), they could go into a common superclass (FreezeThawBase) in continuationFreezeThaw.cpp and removed from ContinuationWrapper altogether.

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PR: https://git.openjdk.java.net/loom/pull/145