RFR: 8160821: VarHandle accesses are penalized when argument conversion is required

[Chen Liang]

Since access descriptor is created for each VH operation site, we can optimistically cache the adapted method handle in a site if the site operates on a constant VH.  Used a C2 IR test to verify such a setup through an inexact VarHandle invocation can be constant folded through (previously, it was blocked by `asType`)

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Commit messages:
 - 8160821

Changes: https://git.openjdk.org/jdk/pull/28585/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28585&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8160821
  Stats: 135 lines in 7 files changed: 104 ins; 20 del; 11 mod
  Patch: https://git.openjdk.org/jdk/pull/28585.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28585/head:pull/28585

PR: https://git.openjdk.org/jdk/pull/28585