RFR: 8361286: Allow enabling of background loading for images loaded from an InputStream [v7]

[John Hendrikx]

> Support background loading of raw input streams
> 
> - Fixed generics (mix up of two ImageLoader types)
> - Removed unused code for handling headers, methods, request parameters
> - Use `long` for progress as streams may exceed 2 GB
> - Improved documentation of Image regarding background loading

John Hendrikx 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 nine additional commits since the last revision:

 - Merge branch 'openjdk:master' into feature/image-constructor
 - Clarify docs
 - Fix formatting
 - Clarify documentation with regards to stream closing
 - Fix typo
 - Add links to progress property in javadoc
 - Remove wrapping
 - Add since tags
 - Support background loading of raw input streams
   
   - Fixed generics (mix up of two ImageLoader types)
   - Removed unused code for handling headers, methods, request parameters
   - Use long for progress as streams max exceed 2 GB
   - Improved documentation of Image regarding background loading

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1875/files
  - new: https://git.openjdk.org/jfx/pull/1875/files/158d1781..71ab9921

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1875&range=06
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1875&range=05-06

  Stats: 149633 lines in 1239 files changed: 80962 ins; 26832 del; 41839 mod
  Patch: https://git.openjdk.org/jfx/pull/1875.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1875/head:pull/1875

PR: https://git.openjdk.org/jfx/pull/1875