[code-reflection] RFR: Lower StringTemplateOp [v2]

[Mourad Abbay]

> The lowering of the StringTemplateOp. We chose not to have a block for every expression body, rather blocks will be created when necessary.

Mourad Abbay has updated the pull request incrementally with two additional commits since the last revision:

 - Update test
 - package up fragments values and expressions values into an array before calling List.of

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Changes:
  - all: https://git.openjdk.org/babylon/pull/39/files
  - new: https://git.openjdk.org/babylon/pull/39/files/2ff32d53..b02575f5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=babylon&pr=39&range=01
 - incr: https://webrevs.openjdk.org/?repo=babylon&pr=39&range=00-01

  Stats: 91 lines in 2 files changed: 71 ins; 7 del; 13 mod
  Patch: https://git.openjdk.org/babylon/pull/39.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/39/head:pull/39

PR: https://git.openjdk.org/babylon/pull/39