RFR: 8295962: Reference to State in Task.java is ambiguous when building with JDK 19 [v2]

[Kevin Rushforth]

> This PR replaces all occurrences of `State` with `Worker.State` in `javafx.concurrent.Task`.
> 
> The `javafx.concurrent.Task` class implements `javafx.concurrent.Worker` and extends `java.util.concurrent.FutureTask`, which in turn implements `java.util.concurrent.Future`.
> 
> `Worker` has a nested `State` enum, which is used in the implementing `Task` class without being qualified -- since `Task` is a `Worker`, we can just say `State` instead of `Worker.State`.
> 
> [JDK-8277090](https://bugs.openjdk.org/browse/JDK-8277090) added a nested `State` enum to the `java.util.concurrent.Future` interface in JDK 19, so an unqualified reference to `State` from the `Task` class is now ambiguous when using JDK 19 to build. The javadoc task fails with an error (and the only reason the javac task doesn't is that we use `--release 17`).
> 
> With this fix, a local build and test using JDK 19 passes.

Kevin Rushforth has updated the pull request incrementally with one additional commit since the last revision:

  Fix unit tests to use Worker.State rather than Task.State

-------------

Changes:
  - all: https://git.openjdk.org/jfx/pull/933/files
  - new: https://git.openjdk.org/jfx/pull/933/files/cfaee2a5..bd46ce12

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=933&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=933&range=00-01

  Stats: 12 lines in 4 files changed: 2 ins; 1 del; 9 mod
  Patch: https://git.openjdk.org/jfx/pull/933.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/933/head:pull/933

PR: https://git.openjdk.org/jfx/pull/933