RFR: 8280377: MethodHandleProxies does not correctly invoke default methods with varags [v4]

[Mandy Chung]

> The MethodHandle of a default method should be made as a fixed arity method handle because it is invoked via Proxy's invocation handle with a non-vararg array of arguments.  On the other hand, the `InvocationHandle::invokeDefault` method  was added in Java 16 to invoke a default method of a proxy instance.  This patch simply converts the implementation to call `InvocationHandle::invokeDefault` instead.

Mandy Chung has updated the pull request incrementally with one additional commit since the last revision:

  add comment

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7185/files
  - new: https://git.openjdk.java.net/jdk/pull/7185/files/30f1a05e..3f31d379

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7185&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7185&range=02-03

  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7185.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7185/head:pull/7185

PR: https://git.openjdk.java.net/jdk/pull/7185