[code-reflection] RFR: Externalizable operations [v4]

[Paul Sandoz]

> Rename `OpWithDefinition` to `ExternalizableOp` and specify as an operation whose contents may be externalized.
> Rename `OpDefintion` to `ExternalizedOp`, enclose in `ExternalizableOp`, and specify it as an operation's externalized content.
> 
> An externaliziable operation may be constructed from its externalized contents, for example by using an operation factory. 
> 
> The method `Op::attributes` is removed, and the method is defined on `ExternalizableOp`. The attribute map returned by the method is the external representation of specific contents of an operation.
> 
> In addition moved `OpDeclaration` to be enclosed within `OpFactory`.

Paul Sandoz has updated the pull request incrementally with one additional commit since the last revision:

  Update Triton example

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

Changes:
  - all: https://git.openjdk.org/babylon/pull/62/files
  - new: https://git.openjdk.org/babylon/pull/62/files/82b490ca..f1024907

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=babylon&pr=62&range=03
 - incr: https://webrevs.openjdk.org/?repo=babylon&pr=62&range=02-03

  Stats: 72 lines in 4 files changed: 0 ins; 2 del; 70 mod
  Patch: https://git.openjdk.org/babylon/pull/62.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/62/head:pull/62

PR: https://git.openjdk.org/babylon/pull/62