[code-reflection] RFR: 8374550: API for casting Value to Op.Result and Block.Parameter [v2]

[Ruby Chen]

> This PR adds two methods, `Value::result()` and `Value::parameter()`, which cast a given Value as a Op.Result or Block.Parameter. If the cast fails, the two methods throw an IllegalStateException.

Ruby Chen has updated the pull request incrementally with one additional commit since the last revision:

  Add tests

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Changes:
  - all: https://git.openjdk.org/babylon/pull/816/files
  - new: https://git.openjdk.org/babylon/pull/816/files/116e4613..616a25ed

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=babylon&pr=816&range=01
 - incr: https://webrevs.openjdk.org/?repo=babylon&pr=816&range=00-01

  Stats: 93 lines in 2 files changed: 89 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/babylon/pull/816.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/816/head:pull/816

PR: https://git.openjdk.org/babylon/pull/816