[code-reflection] Integrated: Reuse some iface mapper types in Schema and remove unused methods

[Gary Frost]

Schema was replicating some work that the iface mapper was already doing.  So reused ifacemapper types.

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Commit messages:
 - Reuse some iface mapper types in Schema and remove unused methods

Changes: https://git.openjdk.org/babylon/pull/172/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=172&range=00
  Stats: 539 lines in 21 files changed: 125 ins; 284 del; 130 mod
  Patch: https://git.openjdk.org/babylon/pull/172.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/172/head:pull/172

PR: https://git.openjdk.org/babylon/pull/172