[code-reflection] RFR: Factory methods should return concrete op

[Paul Sandoz]

The unary/binary/test op factory methods were not returning the concrete operation, which is public, contrary to that of other the factory methods.

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Commit messages:
 - Factory methods should return concrete op.

Changes: https://git.openjdk.org/babylon/pull/842/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=842&range=00
  Stats: 20 lines in 1 file changed: 0 ins; 0 del; 20 mod
  Patch: https://git.openjdk.org/babylon/pull/842.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/842/head:pull/842

PR: https://git.openjdk.org/babylon/pull/842