[code-reflection] Integrated: Refactored MemoryPhases to innerclasses

[Gary Frost]

More phase transform refactoring. 

Re-establishing a pattern where we lean on switches over instance patterns (and inheritance) for phases and ops.

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Commit messages:
 - Refactored MemoryPhases to innerclasses

Changes: https://git.openjdk.org/babylon/pull/626/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=626&range=00
  Stats: 426 lines in 10 files changed: 129 ins; 229 del; 68 mod
  Patch: https://git.openjdk.org/babylon/pull/626.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/626/head:pull/626

PR: https://git.openjdk.org/babylon/pull/626