[code-reflection] RFR: [hat] F16 decoupled from Buffer type

[Juan Fumero]

F16 decoupled from Buffer type.

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Commit messages:
 - [hat] Clarify the special type in the codegen
 - [hat] F16 decoupled from Buffer type

Changes: https://git.openjdk.org/babylon/pull/674/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=674&range=00
  Stats: 63 lines in 10 files changed: 31 ins; 20 del; 12 mod
  Patch: https://git.openjdk.org/babylon/pull/674.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/674/head:pull/674

PR: https://git.openjdk.org/babylon/pull/674