[code-reflection] RFR: Experiment with replacing textual representation in classfile with method that builds the model

[Mourad Abbay]

Experiment with replacing textual representation in classfile with method that builds the model.
Note: This PR is based on changes from #272.

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

Commit messages:
 - Test replacing textual representation with method that builds the code model
 - Add test cases for empty var arg, long and double
 - Move code related to InvokeOp from processOperands(Op).
 - Support bytecode generation for invocation of varArg method

Changes: https://git.openjdk.org/babylon/pull/274/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=274&range=00
  Stats: 268 lines in 4 files changed: 263 ins; 3 del; 2 mod
  Patch: https://git.openjdk.org/babylon/pull/274.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/274/head:pull/274

PR: https://git.openjdk.org/babylon/pull/274