RFR: JDK-8353755 : Add a helper method to Util - findComponent()

[Harshitha Onkar]

`findComponent(final Container container, final Predicate<Component> predicate)` is a useful utility method and thus added to` javax/swing/regtesthelpers/Util.java` instead of having redundant code in tests. It can be used to find a component by label name.

PS: Existing `Util.findSubComponent()` finds component by class name but `findComponent()` can be used to search for a particular component by label name/title when there are multiple subcomponents of same type by applying a predicate logic.

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Commit messages:
 - refactoring changes

Changes: https://git.openjdk.org/jdk/pull/27944/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27944&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8353755
  Stats: 60 lines in 3 files changed: 36 ins; 18 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/27944.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27944/head:pull/27944

PR: https://git.openjdk.org/jdk/pull/27944