[code-reflection] Integrated: Allow arbritrary text to be injected using annotations

[Gary Frost]

We previously allow typdefs and kernel bodies to be injected using annotations on kernels>

Sometimes we want to inject arbitrary chunks of code.  

We can do this with `@Preformatted(" //My text")`

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Commit messages:
 - Allow arbritrary text to be injected using annotations

Changes: https://git.openjdk.org/babylon/pull/633/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=633&range=00
  Stats: 21 lines in 4 files changed: 12 ins; 2 del; 7 mod
  Patch: https://git.openjdk.org/babylon/pull/633.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/633/head:pull/633

PR: https://git.openjdk.org/babylon/pull/633