RFR: 8295078: TextField blurry when inside an TitledPane -> AnchorPane

[Marius Hanl]

The problem here is, that the `AnchorPane` does not use its snapped insets.
Therefore, the fix is to replace all `getInsets().getXXX` calls with their corresponding `snappedXXXInset()` methods.

Note: The reason the `AnchorPane` inside  a `TitledPane` is blurry in the first place is because a `TitledPane` applies padding to its content.
Line 2995 in `modena.css`:

.titled-pane > .content > AnchorPane {
    -fx-padding: 0.8em;
}

which translates to 9.6px.

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Commit messages:
 - 8295078: TextField blurry when inside an TitledPane -> AnchorPane

Changes: https://git.openjdk.org/jfx/pull/910/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=910&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295078
  Stats: 74 lines in 2 files changed: 59 ins; 5 del; 10 mod
  Patch: https://git.openjdk.org/jfx/pull/910.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/910/head:pull/910

PR: https://git.openjdk.org/jfx/pull/910