RFR: 8257164: Share LambdaForms for VH linkers/invokers.

[Vladimir Ivanov]

Introduce sharing of `LambdaForms` for `VarHandle` linkers and invokers.
It reduces the number of LambdaForms needed at runtime.

Testing: tier1-4

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Commit messages:
 - Share LambdaForms for VH linkers/invokers.

Changes: https://git.openjdk.java.net/jdk/pull/1455/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1455&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257164
  Stats: 48 lines in 3 files changed: 21 ins; 10 del; 17 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1455.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1455/head:pull/1455

PR: https://git.openjdk.java.net/jdk/pull/1455