RFR: 8289853: Update HarfBuzz to 4.4.1

[Phil Race]

This upgrades the JDK's version of harfbuzz to 4.4.1. The current version is 2.8.0
Builds on all platforms. Testing looks good.
I've added an UPDATING.txt file with tips on the steps involved in these upgrades.

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Commit messages:
 - 8289853
 - 8289853

Changes: https://git.openjdk.org/jdk/pull/9420/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9420&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8289853
  Stats: 58001 lines in 275 files changed: 32096 ins; 18824 del; 7081 mod
  Patch: https://git.openjdk.org/jdk/pull/9420.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9420/head:pull/9420

PR: https://git.openjdk.org/jdk/pull/9420