RFR: 8268592: JDK-8262891 causes an NPE in Lint.augment

[Liam Miller-Cushon]

Avoid descending into lambdas in `Flow.aliveAfter`, since the lambda won't affect the result,
and to avoid descending into lambda bodies that haven't been attributed yet when `aliveAfter`
is used while attributing switches.

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Commit messages:
 - 8268592: JDK-8262891 causes an NPE in Lint.augment

Changes: https://git.openjdk.java.net/jdk/pull/4502/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4502&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268592
  Stats: 65 lines in 2 files changed: 65 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4502.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4502/head:pull/4502

PR: https://git.openjdk.java.net/jdk/pull/4502