[code-reflection] RFR: Enhance OpWriter [v3]

[Paul Sandoz]

> Enhance OpWriter to support the following options
> 1. Drop an operation's descendants. This allows for writing just the operation "header".
> 2. Write an operation's result even if it is void. This allows for improved debugging and presentation in some cases, esp. when we refer to values uniformly (an operation whose result is void still has a value, just one that is not used.)
> 
> Also, consolidate the write operations, and remove the explicit insertion of a live feed at the end of writing an operation.

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

  Add test

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Changes:
  - all: https://git.openjdk.org/babylon/pull/79/files
  - new: https://git.openjdk.org/babylon/pull/79/files/99071aad..a5489e56

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=babylon&pr=79&range=02
 - incr: https://webrevs.openjdk.org/?repo=babylon&pr=79&range=01-02

  Stats: 73 lines in 1 file changed: 73 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/babylon/pull/79.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/79/head:pull/79

PR: https://git.openjdk.org/babylon/pull/79