[code-reflection] Integrated: Isolating iface mapper so it can be used outside of HAT

[Gary Frost]

Ideally we can use iface mapper and schema builder (iface -> MemoryLayout) outside of HAT

This is the first step to that end.

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

Commit messages:
 - Isolating iface mapper so it can be used outside of HAT

Changes: https://git.openjdk.org/babylon/pull/760/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=760&range=00
  Stats: 623 lines in 63 files changed: 217 ins; 275 del; 131 mod
  Patch: https://git.openjdk.org/babylon/pull/760.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/760/head:pull/760

PR: https://git.openjdk.org/babylon/pull/760