[code-reflection] RFR: Lower StringTemplateOp [v7]

[Mourad Abbay]

> The lowering of the StringTemplateOp.

Mourad Abbay has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:

 - Merge branch 'code-reflection' into lower-string-template
 - Apply recommendations
 - Apply recommendations
 - Lower each expression in a separate block
 - Rename J_L_LIST to J_U_LIST
 - Update test
 - package up fragments values and expressions values into an array before calling List.of
 - Lower StringTemplateOp

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Changes:
  - all: https://git.openjdk.org/babylon/pull/39/files
  - new: https://git.openjdk.org/babylon/pull/39/files/afc65407..a9baa53e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=babylon&pr=39&range=06
 - incr: https://webrevs.openjdk.org/?repo=babylon&pr=39&range=05-06

  Stats: 3409 lines in 24 files changed: 3371 ins; 3 del; 35 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