RFR: 8081507: Open or Save button in JFileChooser has OK title in GTK LaF

Tue Dec 27 19:15:59 UTC 2022

Open or Save button in JFileChooser has OK title in GTK LAF. The open/save button text modified as per the native FileChooser. Manual test case is added.

`open/test/jdk/sanity/client/SwingSet/src/FileChooserDemoTest.java` failed with the current fix with an exception `**Wait AbstractButton with text "OK" loaded.**` Updated the test for GTK LAF and tested in CI which is OK now.

CI link is added in JBS.

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Commit messages:
 - Open/Save button text modified

Changes: https://git.openjdk.org/jdk/pull/11790/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11790&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8081507
  Stats: 82 lines in 3 files changed: 78 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/11790.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11790/head:pull/11790

PR: https://git.openjdk.org/jdk/pull/11790