RFR: 8333236: Test java/foreign/TestAccessModes.java is timing out after passing [v2]

[Maurizio Cimadamore]

> This PR restores a var handle cache in `Utils::makeSegmentViewVarHandle`. The cache was moved to `ValueLayouts::varHandle` as part of [pull/19251](https://git.openjdk.org/jdk/pull/19251), on the basis that we want to optimize the common case like:
> 
> 
> ValueLayout layout = ...
> layout.varHandle().get(...)
> 
> 
> And that caching more complex var handles didn't seem to add value, given that, for these var handles, the logic in `LayoutPath` needs to adapt the returned var handle anyways.
> 
> But, `TestAccessModes` revealed a different picture - w/o any cache in `Utils` the test end up allocating 8963 var handle instances (instead of just 4), in each of the 4 runs the test includes. While this is admittedly a stress test, it seems nice to restore the level of sharing we had before [pull/19251](https://git.openjdk.org/jdk/pull/19251).

Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:

  Address review comments

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/19485/files
  - new: https://git.openjdk.org/jdk/pull/19485/files/b37f9cc9..3b2a3380

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19485&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19485&range=00-01

  Stats: 18 lines in 2 files changed: 14 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/19485.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19485/head:pull/19485

PR: https://git.openjdk.org/jdk/pull/19485