RFR: 8284993: Replace System.exit call in swing tests with RuntimeException [v4]

[Prasanta Sadhukhan]

> Few swing tests call System.exit() which might stop the test harness from executing further tests if any of the test fail. We should replace with RuntimeException.

Prasanta Sadhukhan has updated the pull request incrementally with one additional commit since the last revision:

  throw exception in main

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8293/files
  - new: https://git.openjdk.java.net/jdk/pull/8293/files/2c8508a6..7d49634d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8293&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8293&range=02-03

  Stats: 23 lines in 1 file changed: 5 ins; 3 del; 15 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8293.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8293/head:pull/8293

PR: https://git.openjdk.java.net/jdk/pull/8293