RFR: 8267551: Support loading images from inline data-URIs [v11]

[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 with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 13 additional commits since the last revision:

 - Merge branch 'openjdk:master' into feature/image-datauri
 - Rename DataURI.isValidURI
 - Reverted a change
 - Allow leading and trailing whitespace in data URI
 - Removed test
 - Changed data URI detection
 - Merge branch 'master' into feature/image-datauri
 - Moved test
 - Added javadoc
 - Added javadoc
 - ... and 3 more: https://git.openjdk.java.net/jfx/compare/fc92ab9f...f6878f51

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Changes:
  - all: https://git.openjdk.java.net/jfx/pull/508/files
  - new: https://git.openjdk.java.net/jfx/pull/508/files/edb6f658..f6878f51

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=508&range=10
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=508&range=09-10

  Stats: 559 lines in 12 files changed: 386 ins; 145 del; 28 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