[code-reflection] RFR: Add ConstructorRef

[Mourad Abbay]

This is Maurizio's work.
This PR tries to make `NewOp` similar to how `InvokeOp` is designed. It does this by adding a descriptor for constructors: `ConstructorRef`.
`ConstructorRef` is wrapper around `FunctionType`, providing functionalities for resolution to a reflective instance.
Some changes are common between this PR and #393.

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Commit messages:
 - Remove trailing whitespaces
 - No need to pass refType during creation of ConstructorRef
 - Merge branch 'code-reflection' into new_op_constr_ref
 - Enhance ConstructorRef::resolveToHandle to cover array creation
 - Merge branch 'code-reflection' into new_op_constr_ref
 - Merge branch 'code-reflection' into new_op_constr_ref
 - Clean up CodeModelToAST
 - Fix tests
 - Initial push
 - Cleanup code in CodeModelToAST

Changes: https://git.openjdk.org/babylon/pull/395/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=395&range=00
  Stats: 569 lines in 28 files changed: 386 ins; 65 del; 118 mod
  Patch: https://git.openjdk.org/babylon/pull/395.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/395/head:pull/395

PR: https://git.openjdk.org/babylon/pull/395