RFR: 7903961: Make default timeout configurable [v2]

[Christian Stein]

> Please review this change replacing the hard-coded `120` seconds default timeout for test actions with a configurable solution parsing a custom default value from `TEST.ROOT` and `TEST.properties` files:
> 
> 
> timeout.default.seconds=360
> 
> 
> Especially in combination with "JUnit.dirs" and "TestNG.dirs", where all actions directives found in a test file are ignored, is helpful.

Christian Stein has updated the pull request incrementally with one additional commit since the last revision:

  Simplify implementation, don't expose default timeout value

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

Changes:
  - all: https://git.openjdk.org/jtreg/pull/253/files
  - new: https://git.openjdk.org/jtreg/pull/253/files/621abbb4..b9c04050

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jtreg&pr=253&range=01
 - incr: https://webrevs.openjdk.org/?repo=jtreg&pr=253&range=00-01

  Stats: 61 lines in 6 files changed: 3 ins; 55 del; 3 mod
  Patch: https://git.openjdk.org/jtreg/pull/253.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/253/head:pull/253

PR: https://git.openjdk.org/jtreg/pull/253