RFR: 8269806: Emoji rendering on Linux [v9]

[Nikita Gubarkov]

> It was implemented in JetBrains Runtime a year ago and was ported & refactored for this PR
> It includes:
> - Bitmap glyph loading via Freetype
> - Manual scaling & transformation of bitmap glyphs with nearest-neighbor or bilinear-mipmap style algorithms depending on the text antialiasing hint
> - Storing BGRA glyphs in glyph cache & rendering them as plain images, as currently used XRender text drawing functions doesn't support colored glyphs
> - Small fixes in related code like null-checks which could cause NPE & comment typos

Nikita Gubarkov has updated the pull request incrementally with one additional commit since the last revision:

  Optimize bitmap creation in GlyphRenderData
  
  Get rid of unneeded abstract methods
  
  Use SSIM for OutlineTextRendererEmoji test

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/4798/files
  - new: https://git.openjdk.org/jdk/pull/4798/files/29b68f14..1a2b4d6a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=4798&range=08
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=4798&range=07-08

  Stats: 243 lines in 11 files changed: 130 ins; 64 del; 49 mod
  Patch: https://git.openjdk.org/jdk/pull/4798.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/4798/head:pull/4798

PR: https://git.openjdk.org/jdk/pull/4798