RFR: 8316285: Opensource JButton manual tests [v2]

[Abhishek Kumar]

> Few closed JButton swing manual test converted to automated and open sourced.

Abhishek Kumar has updated the pull request incrementally with one additional commit since the last revision:

  Removed unused robot instance

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15835/files
  - new: https://git.openjdk.org/jdk/pull/15835/files/0043dc59..802eadb9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15835&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15835&range=00-01

  Stats: 3 lines in 3 files changed: 0 ins; 3 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15835.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15835/head:pull/15835

PR: https://git.openjdk.org/jdk/pull/15835