[11u] RFR: 8220231: Cache HarfBuzz face object for same font's text layout calls

[Lindenmaier, Goetz]

Hi,

i would like to downport this change for parity with 11.0.6-oracle.
I had to resolve two files, both trivial:

src/java.desktop/share/classes/sun/font/FreetypeFontScaler.java
One patch did not apply due to a difference in a comment in the context.

src/java.desktop/share/native/libfontmanager/hb-jdk-font.cc
A huge chunk could not get applied. This is because tiny
"8223886: Add in font table referene" was applied after
this change in jdk/jdk, but was already downported to 11u-dev,
so it comes there first.
The version history of this file in 11 and 14 is exactly the
same, I resolved the conflict so that the files look alike.

webrev: http://cr.openjdk.java.net/~goetz/wr19/8220231-cache_harfbuzz-jdk11/01/
bug: https://bugs.openjdk.java.net/browse/JDK-8220231
orig change: http://hg.openjdk.java.net/jdk/jdk/rev/98473958d49a
The conflicting change is closed, unfortunately:
8223886: Add in font table referene
http://hg.openjdk.java.net/jdk-updates/jdk11u-dev/rev/174afa5802bd

Best regards,
  Goetz