RFR: JDK-8286311: remove boilerplate from use of runTests [v2]

[Jonathan Gibbons]

> Please review a test-only cleanup for JDK 21.
> 
> There are two mostly-automated (IDE) changes here:
> 
> 1. Remove redundant boiler-plate arguments from calls to `JavadocTester.runTests()`.  The use of a function to derive and provide a method-specific directory because unnecessary with JDK-
> 2. Use `var` for the declaration of the `tester` variable found in the `main` method of most javadoc tests.
> 
> The changes were mostly done with IDEA _Replace in Files..._, with some manual fixup for some outlying cases found while checking the code.

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

  update copyrights

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/11746/files
  - new: https://git.openjdk.org/jdk/pull/11746/files/877d4470..59d9946f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11746&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11746&range=00-01

  Stats: 214 lines in 214 files changed: 0 ins; 0 del; 214 mod
  Patch: https://git.openjdk.org/jdk/pull/11746.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11746/head:pull/11746

PR: https://git.openjdk.org/jdk/pull/11746