RFR: 8373038: Interpolator factories should follow method naming convention [v3]

[Michael Strauß]

> The following interpolator factories don't follow the standard method naming convention:
> 
> * `Interpolator.SPLINE(double, double, double, double)`
> * `Interpolator.TANGENT(Duration, double, Duration, double)`
> * `Interpolator.TANGENT(Duration, double)`
> * `Interpolator.STEPS(int, StepPosition)`
> 
> New methods named `ofSpline`, `ofTangent`, and `ofSteps` are added. The existing methods are deprecated (not for removal) in favor of the correctly-named methods. This change is in line with the new `ofLinear` method added with #1977.

Michael Strauß has updated the pull request incrementally with one additional commit since the last revision:

  replace reference to STEPS

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1996/files
  - new: https://git.openjdk.org/jfx/pull/1996/files/2128f2a9..42dbd19e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1996&range=02
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1996&range=01-02

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jfx/pull/1996.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1996/head:pull/1996

PR: https://git.openjdk.org/jfx/pull/1996