RFR: 8285698: Create a test to check the focus stealing of JPopupMenu from JComboBox [v2]

[Manukumar V S]

> This test verifies that showing a JPopupMenu shouldn't steal the focus out of current focused component..
> This fix moves an unstable closed test to open but updated to be more comprehensive in testing multiple Look and Feels and with some stabilisation improvements. The closed test had some dependencies with some proprietary libraries which are all removed here.
> 
> Testing:
> Tested using mach5 10 times per platform and got all Pass.

Manukumar V S has updated the pull request incrementally with one additional commit since the last revision:

  Review comment fixed: Removed finally block and added the call to disposeFrame() before the exception is thrown

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8426/files
  - new: https://git.openjdk.java.net/jdk/pull/8426/files/b22649d6..1c2230b2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8426&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8426&range=00-01

  Stats: 7 lines in 1 file changed: 1 ins; 5 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8426.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8426/head:pull/8426

PR: https://git.openjdk.java.net/jdk/pull/8426