RFR: 8255002: Many javafx.controls unit tests have incorrect name containing impl_*

[Ajit Ghaisas]

It is a test cleanup work.

Issue :
Many unit tests in javafx.controls module have incorrect naming that use text "impl_" in names and comments.
The test code correctly avoids using impl_* methods (as they were removed in JDK 9), but test names still have "impl_"
in them.

Fix :
These tests are renamed by replacing impl_* with appropriate css method.

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Commit messages:
 - JDK-8255002 - rename tests

Changes: https://git.openjdk.java.net/jfx/pull/326/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=326&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255002
  Stats: 139 lines in 20 files changed: 0 ins; 0 del; 139 mod
  Patch: https://git.openjdk.java.net/jfx/pull/326.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/326/head:pull/326

PR: https://git.openjdk.java.net/jfx/pull/326