RFR: 8278134: Move static utility methods to infrastructure (EditAndScrollTest) [v2]

[Jeanette Winzenburg]

> Extracted static test utility methods from EditAndScrollTest into new VirtualizedControlTestUtils, added rudimentary tests for the methods.

Jeanette Winzenburg has updated the pull request incrementally with one additional commit since the last revision:

  fixed c&p error in doc

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Changes:
  - all: https://git.openjdk.java.net/jfx/pull/690/files
  - new: https://git.openjdk.java.net/jfx/pull/690/files/c2642bbe..1f2a9815

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=690&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=690&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jfx/pull/690.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/690/head:pull/690

PR: https://git.openjdk.java.net/jfx/pull/690