RFR: JDK-8324182 Deprecate for removal SimpleSelector and CompoundSelector classes [v5]

[John Hendrikx]

> The SimpleSelector and CompoundSelector classes are public classes in an exported package, javafx.css, but they are not intended to be used by applications. They are implementation details. They cannot be constructed directly and no other JavaFX API accepts or returns a SimpleSelector or CompoundSelector.
> 
> We should deprecate them for removal so we can move them to a non-exported package, removing them from the public API.

John Hendrikx has updated the pull request incrementally with one additional commit since the last revision:

  Use getStyleClassNames

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1340/files
  - new: https://git.openjdk.org/jfx/pull/1340/files/631ca587..117a8025

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1340&range=04
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1340&range=03-04

  Stats: 5 lines in 3 files changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jfx/pull/1340.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1340/head:pull/1340

PR: https://git.openjdk.org/jfx/pull/1340