<AWT Dev> RFR: 8269806: Emoji rendering on Linux

[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

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Commit messages:
 - 8269806: Emoji rendering on Linux

Changes: https://git.openjdk.java.net/jdk/pull/4798/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4798&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8269806
  Stats: 749 lines in 9 files changed: 555 ins; 51 del; 143 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