RFR: 8269806: Emoji rendering on Linux [v3]

[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:

  8269806: Fix emoji rendering with -Dsun.java2d.xrender=false and AA=OFF

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4798/files
  - new: https://git.openjdk.java.net/jdk/pull/4798/files/5d99aee6..9dbed75f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4798&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4798&range=01-02

  Stats: 37 lines in 3 files changed: 23 ins; 0 del; 14 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4798.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4798/head:pull/4798

PR: https://git.openjdk.java.net/jdk/pull/4798