RFR: 8246104: Some complex text doesn't render correctly on macOS

[Phil Race]

This PR addresses some font problems on macOS.
(1) Garbled Arabic with the System font
(2) Non-ideal fallback fonts for all fonts
(3) No bold for System font.

In particular the standard System Font was garbling Arabic text - random glyphs from another font.
The root of this issue is that several releases ago macOS introduced UI fonts that are hidden from
enumeration. must be loaded by a special API and cannot be loaded by name, even if you extract
the name from the core text font loaded by that special API.
These fonts usually have a name that begins with "." such as the postscript name ".AppleUISystemFont"
and "name" for the main instance of this will be "System Font Regular". These live in files called "SFNS.ttf"
and "SFArabic.ttf" and similar.

JavaFX has its own "System" font family logical name and in order to map to the macOS system font,
several releases ago we started using the special API referenced above.

Normally we have our own list of fall back fonts for other scripts.
But when we encounter complex scripts such as Arabic, and ask CoreText to layout the glyphs,
it may use other system fonts for Arabic (eg ".SFArabic") and the FX code dynamically adds
this new font to its fallback list - by name.
But this new font can't be directly referenced by name either, but that's what used to work and the FX code tries.

So to fix this we need to grab the reference to the font that was returned by CoreText and use
that to create the PrismFont we add as a fall back.
The code that first recognises it needs to go this route is in CTGlyphLayout.java when
"getSlotForFont(String name") fails.
Instead it calls new code in CTFactory which in turn calls a new constructor and supporting code in CTFontFile.java.
There's also supporting changes in native code - coretext.c

Additionally to support that when we ask the platform to enumerate fallbacks, we might get such "." fonts,
we need to make some more changes
Now on to more "fallback" enhancements.
Prior to this fix, on macOS we had a short, hard-coded global list.
This fix calls the macOS API to get the cascading fallback list for a font.
This improves the fallback behaviour in respect to providing
(1) More appropriate styles, (2) More supported code pointd, (3) Code point support coming from a preferred font.
There was some desirable re-factoring as part of this, as the location of fallbacks was pushed from
"if <windows> else if <linux> else <mac> in shared code, down into the appropriate platform factory

This also made it easier to do some required changes to allow fallbacks to be pre-initialised with the
native font resource, not just a name+ file. The new class FontFallbackInfo encapsulates this and changes
were made to follow it.
In practice on macOS it seems that some "." cascading fallbacks for the "." system font come with a "NULL"
file name. Without being able to identify the file we aren't able to use the font to skip them.
More changes would be needed to provide a PrismFont subclass that can handle this case.
Fortunately that isn't happening for any of the fallbacks we get from complex text layout.

The final thing this fixes is that "System Bold" was the same as "System Regular".
The needed name getting lost along the way to constructing the native font.

The work done here also highlighted that we really need to add code that at least recognises OpenType variation fonts.
And some day after that we could expose API that allows apps to request non-named variations.

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

Commit messages:
 - fix bold detection
 - Remove more trailing whitespace
 - Remove trailing whitespace
 - Remove commented line
 - Update windows JNI names
 - Merge branch 'master' of github.com:prrace/jfx into arabic_etc
 - Fix bold italic
 - 8246104

Changes: https://git.openjdk.org/jfx/pull/1067/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1067&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8246104
  Stats: 877 lines in 20 files changed: 652 ins; 155 del; 70 mod
  Patch: https://git.openjdk.org/jfx/pull/1067.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1067/head:pull/1067

PR: https://git.openjdk.org/jfx/pull/1067