RFR: 8043179: Lambda expression can mutate final field [v4]

[Archie L. Cobbs]

> This patch causes lambdas to be treated like non-constructor methods with respect to field initialization in `Flow.AssignAnalyzer`.
> 
> This fixes [JDK-8043179](https://bugs.openjdk.org/browse/JDK-8043179); the test program in the bug now gives this:
> 
> LambdaFieldInit.java:6: error: variable x might already have been assigned
>         Runnable r1 = () -> x = "hi";
>                             ^
> 
> 
> This also aligns the compiler with the proposed spec fix in [JDK-8043176](https://bugs.openjdk.org/browse/JDK-8043176) and fixes the inconsistency between lambdas and inner class methods shown [here](https://stackoverflow.com/questions/39881295/why-are-java-lambdas-treated-differently-from-nested-classes-with-respect-to-ins).

Archie L. Cobbs has updated the pull request incrementally with one additional commit since the last revision:

  Fix @author in test to match github username per instructions.

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/10381/files
  - new: https://git.openjdk.org/jdk/pull/10381/files/6ae0fca3..b7bc0b6d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10381&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10381&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10381.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10381/head:pull/10381

PR: https://git.openjdk.org/jdk/pull/10381