RFR: 8296330: Tests: Add layout container snapping tests [v3]

[Marius Hanl]

> While checking https://bugs.openjdk.org/browse/JDK-8295078 I found much more layout container which do not snap their children correctly.
> 
> The goal of this PR is to add snapping tests for all layout container.
> After that we can create issues for all broken layout container, fix them and comment in the corresponding line.

Marius Hanl has updated the pull request incrementally with one additional commit since the last revision:

  8296330: Missed two :P

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Changes:
  - all: https://git.openjdk.org/jfx/pull/936/files
  - new: https://git.openjdk.org/jfx/pull/936/files/83080ec6..2d5e5801

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=936&range=02
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=936&range=01-02

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jfx/pull/936.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/936/head:pull/936

PR: https://git.openjdk.org/jfx/pull/936