[code-reflection] RFR: Invocation to vararg methods

[Paul Sandoz]

Re-consolidate to one invocation operation that explicitly declares its invoke kind and whether it is an invocation to a varargs method.

Resolution of a method reference accepts an invoke kind. The ambiguity when resolving a method reference without an invoke kind has been cleared up, in these cases we can only resolve to a direct method, one in which the referencing class is the class that declares the method.

I managed to avoid numerous changes to update the text models in language tests. Creating an invoke operation from external form is permissive in the attributes that are present. It makes the same assumptions as the invoke factory method in determining the invocation kind from the argument count and invoke descriptor count, and assumes the method is not a varargs method (the common case).

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Commit messages:
 - Undo edits.
 - Avoid generating attributes
 - Invocation to vararg methods.

Changes: https://git.openjdk.org/babylon/pull/225/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=225&range=00
  Stats: 636 lines in 15 files changed: 421 ins; 118 del; 97 mod
  Patch: https://git.openjdk.org/babylon/pull/225.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/225/head:pull/225

PR: https://git.openjdk.org/babylon/pull/225