RFR: JDK-8307301: Update HarfBuzz to 7.2.0

[Harshitha Onkar]

Harfbuzz updated from 7.0.1 to 7.2.0.

Files changed -

- harfbuzz.md file updated
- 1 newly added source file - hb-ot-var-cvar-table.hh
- 73 modified source files


Following testing was carried for the update and works as expected. 

1. Client CI Testing
2. TextLayout related tests
3. Font2DTest in TextLayout mode
4. Manual Testing of Arabic, Hebrew, Thai, Indic languages on TextLayout. (Mac, Windows and Linux)

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Commit messages:
 - removed whitespaces
 - added .md file
 - modified files
 - newly added file

Changes: https://git.openjdk.org/jdk/pull/13835/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13835&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307301
  Stats: 2679 lines in 75 files changed: 1972 ins; 424 del; 283 mod
  Patch: https://git.openjdk.org/jdk/pull/13835.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13835/head:pull/13835

PR: https://git.openjdk.org/jdk/pull/13835