RFR: 8267551: Support loading images from inline data-URIs [v18]

[Michael Strauß]

> This PR adds support for loading images from [inline data URIs](https://en.wikipedia.org/wiki/Data_URI_scheme), which is also widely supported by web browsers. This enables developers to package small images in CSS files, rather than separately deploying the images alongside the CSS file.

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

  changes as per review

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

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/508/files
  - new: https://git.openjdk.java.net/jfx/pull/508/files/ed498ef6..5cbfa701

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=508&range=17
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=508&range=16-17

  Stats: 23 lines in 2 files changed: 13 ins; 8 del; 2 mod
  Patch: https://git.openjdk.java.net/jfx/pull/508.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/508/head:pull/508

PR: https://git.openjdk.java.net/jfx/pull/508