RFR: JDK-8272853: improve `JavadocTester.runTests` [v3]

[Jonathan Gibbons]

> Please review a medium simple test-only fix to improve the `JavadocTester` `runTests` methods.
> 
> Currently, there are two overloads: one to invoke no-args test methods, and another to invoke test methods with args, such as a method-specific `Path`.  This latter one is slightly inconvenient to use, since it requires the boilerplate use of a function to create the arguments.
> 
> The first overload is updated in a backwards compatible way, to examine the parameters of methods annotated with `@Test`, and to recognize common patterns: namely no-args methods and `(Path)` methods, without the need for any additional function.  The second overload is retained by backwards compatibility, until if and when we decide it is no longer required.
> 
> In addition, two new overloads are added, similar to the first two, but with the addition of an extra parameter to decide which methods should be invoked. This is primarily a debugging aid.  Using these overloads, it is easy to specify, on the command line used to run the test, the methods to be executed.
> 
> A new test is added to test the new functionality.

Jonathan Gibbons has updated the pull request incrementally with one additional commit since the last revision:

  weaken conditions for when IllegalArgumentException may be thrown

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6983/files
  - new: https://git.openjdk.java.net/jdk/pull/6983/files/ee672346..5fbaeb03

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6983&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6983&range=01-02

  Stats: 12 lines in 1 file changed: 10 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6983.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6983/head:pull/6983

PR: https://git.openjdk.java.net/jdk/pull/6983