RFR: 8336491: Unnecessary boxing conversions in void-returning lambdas [v2]

[Liam Miller-Cushon]

> Please consider this possible fix for [JDK-8336491](https://bugs.openjdk.org/browse/JDK-8336491), which avoids generating an unnecessary boxing conversion for the result of void-returning expression lambdas.

Liam Miller-Cushon has updated the pull request incrementally with one additional commit since the last revision:

  Push fix into boxIfNeeded, other callers pass a VOID type

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20222/files
  - new: https://git.openjdk.org/jdk/pull/20222/files/7f4337e5..3f319f11

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20222&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20222&range=00-01

  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/20222.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20222/head:pull/20222

PR: https://git.openjdk.org/jdk/pull/20222