[code-reflection] RFR: Some HAT cleanups [v3]

[Paul Sandoz]

> - Fix hatrun.sh to use the correct paths (i think they are corrected, and verified for my local build)
> - Enhance  CMakeLists.txt to check if BEEHIVE env is set, so as not to hardcode the location
> - Use more idiomatic code model APIs (some added based on HAT feedback)

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

  Fix some typos.

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Changes:
  - all: https://git.openjdk.org/babylon/pull/141/files
  - new: https://git.openjdk.org/babylon/pull/141/files/83013e50..718eca47

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=babylon&pr=141&range=02
 - incr: https://webrevs.openjdk.org/?repo=babylon&pr=141&range=01-02

  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/babylon/pull/141.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/141/head:pull/141

PR: https://git.openjdk.org/babylon/pull/141