RFR: 8377427: Reduce substring allocations in Color.web(String, double) [v8]

[Michael Strauß]

> Color.web(string, double) parses a color string by creating substrings of the input. These string allocations can be removed.
> 
> CSS numbers are parsed by `CssNumberParser`, which parses CSS-compliant numbers using Lemire's algorithm.
> 
> There are no new tests for the `Color` class, since the existing tests already cover all relevant code paths.

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

  use precomputed powers of five, more tests

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/2069/files
  - new: https://git.openjdk.org/jfx/pull/2069/files/340c1825..48d1e0fc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=2069&range=07
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=2069&range=06-07

  Stats: 394 lines in 2 files changed: 307 ins; 14 del; 73 mod
  Patch: https://git.openjdk.org/jfx/pull/2069.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/2069/head:pull/2069

PR: https://git.openjdk.org/jfx/pull/2069