[code-reflection] RFR: Unify common code of SwitchStatementOp and SwitchExpressionOp

[Mourad Abbay]

Unify common code of SwitchStatementOp and SwitchExpressionOp.

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Commit messages:
 - Refactor

Changes: https://git.openjdk.org/babylon/pull/222/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=222&range=00
  Stats: 274 lines in 1 file changed: 74 ins; 190 del; 10 mod
  Patch: https://git.openjdk.org/babylon/pull/222.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/222/head:pull/222

PR: https://git.openjdk.org/babylon/pull/222