RFR: 8176501: Method Shape.getBounds2D() incorrectly includes Bezier pts

[Jeremy]

This removes code that relied on consulting the Bezier control points to calculate the Rectangle2D bounding box. Instead it's pretty straight-forward to convert the Bezier control points into the x & y parametric equations. At their most complex these equations are cubic polynomials, so calculating their extrema is just a matter of applying the quadratic formula to calculate their extrema. (Or in path segments that are quadratic/linear/constant: we do even less work.)

The bug writeup indicated they wanted Path2D#getBounds2D() to be more accurate/concise. They didn't explicitly say they wanted CubicCurve2D and QuadCurve2D to become more accurate too. But a preexisting unit test failed when Path2D#getBounds2D() was updated and those other classes weren't. At this point I considered either:
A. Updating CubicCurve2D and QuadCurve2D to use the new more accurate getBounds2D() or
B. Updating the unit test to forgive the discrepancy.

I chose A. Which might technically be seen as scope creep, but it feels like a more holistic/better approach.

Other shapes in java.awt.geom should not require updating, because they already identify concise bounds.

This also includes a new unit test (in Path2D/UnitTest.java) that fails without the changes in this commit.

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

Commit messages:
 - 8176501: Method Shape.getBounds2D() incorrectly includes Bezier control points in bounding box

Changes: https://git.openjdk.java.net/jdk/pull/6227/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6227&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8176501
  Stats: 482 lines in 5 files changed: 349 ins; 130 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6227.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6227/head:pull/6227

PR: https://git.openjdk.java.net/jdk/pull/6227