RFR: JDK-8270476: Make floating-point test infrastructure more lambda and method reference friendly [v3]

[Joe Darcy]

> Update the java.lang.{Math, StrictMath} regression test helper library to accept method references. This allows the test programs to be DRY-er as the inputs to the method under test don't have to be repeated. The float test method were not updated due to limitations in type inference if both float and double methods with functional interface parameters are present.
> 
> Also did some general tidying up for the test code.

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

  Respond to review feedback.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7216/files
  - new: https://git.openjdk.java.net/jdk/pull/7216/files/789782ce..30987b71

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7216&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7216&range=01-02

  Stats: 7 lines in 3 files changed: 3 ins; 2 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7216.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7216/head:pull/7216

PR: https://git.openjdk.java.net/jdk/pull/7216