RFR: 8267162 Add jtreg test group definitions for langtools

[Maurizio Cimadamore]

This patch adds test group definitions for langtools, so that langtools tests can be more easily discovered when running make.

For instance, with this patch, typing:


$ make run-test-langtools_


and then hit tab (on Linux) reveals the following possible completions:


run-test-langtools_all                   run-test-langtools_javac                 run-test-langtools_javadoc               run-test-langtools_javap                 run-test-langtools_jdeprscan             run-test-langtools_jdeps                 run-test-langtools_jshell                run-test-langtools_jshell_unstable       run-test-langtools_sjavac
run-test-langtools_all-only              run-test-langtools_javac-only            run-test-langtools_javadoc-only          run-test-langtools_javap-only            run-test-langtools_jdeprscan-only        run-test-langtools_jdeps-only            run-test-langtools_jshell-only           run-test-langtools_jshell_unstable-only  run-test-langtools_sjavac-only


(the `-only` targets are added by make - the others are the ones added by this patch).

I've added a group for every major tool:

* javac
* javadoc
* jshell
* javap
* jdeps
* jdeprscan
* sjavac

Plus a target (`langtools_all`) which runs all langtools test. For every tool target, the group also run shared tests (e.g. the coding rules tests).

I also reorganized tier1 and tier2 groups a little: both tiers were referring to a group of jshell tests which is less stable than the others, so has been moved to tier2. Instead of repeating the list of test twice, I've defined away the list of unstable test in a group, `langtools_jshell_unstable` and then defined tier1 as `langtools_all - langtools_jshell_unstable` while tier2 is defined as simply `langtools_jshell_unstable`.

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Commit messages:
 - Add test groups for langtools
 - Initial push

Changes: https://git.openjdk.java.net/jdk/pull/4033/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4033&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8267162
  Stats: 65 lines in 1 file changed: 43 ins; 15 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4033.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4033/head:pull/4033

PR: https://git.openjdk.java.net/jdk/pull/4033