[code-reflection] RFR: Some HAT cleanups [v2]

[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:

  Revert changes to hatrun.bash

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

Changes:
  - all: https://git.openjdk.org/babylon/pull/141/files
  - new: https://git.openjdk.org/babylon/pull/141/files/ba7d9ea0..83013e50

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=babylon&pr=141&range=01
 - incr: https://webrevs.openjdk.org/?repo=babylon&pr=141&range=00-01

  Stats: 38 lines in 1 file changed: 0 ins; 12 del; 26 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