RFR: JDK-8290901: Reduce use of -source in langtools tests [v5]

[Joe Darcy]

> To a first approximation, this change replaces use of "-source", where possible, with the preferable "--release" javac option. (There are cases where this swap is not desirable, such as when newer library features are being used in the test.)
> 
> A few unneeded uses of -source were removed entirely.
> 
> I'll update copyrights before any push.

Joe Darcy has updated the pull request incrementally with one additional commit since the last revision:

  Fix bug found in code review.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9622/files
  - new: https://git.openjdk.org/jdk/pull/9622/files/f24c3f6c..54554767

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9622&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9622&range=03-04

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9622.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9622/head:pull/9622

PR: https://git.openjdk.org/jdk/pull/9622