RFR: JDK-8305885: Use ReadOnly*PropertyBase class where possible

[John Hendrikx]

These changes use base classes for custom properties where possible for the `ExpressionHelper` logic (and in one case, all the bind logic as well) instead of duplicating these each time. As the base classes receive far more scrutiny, this should reduce bugs in these re-implementations.

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Commit messages:
 - Use base classes where possible

Changes: https://git.openjdk.org/jfx/pull/1092/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1092&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305885
  Stats: 394 lines in 8 files changed: 73 ins; 253 del; 68 mod
  Patch: https://git.openjdk.org/jfx/pull/1092.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1092/head:pull/1092

PR: https://git.openjdk.org/jfx/pull/1092