RFR: JDK-8301998: Update HarfBuzz to 7.0.1

[Harshitha Onkar]

HarfBuzz library updated from v4.4.1 to v7.0.1

- harfbuzz.md file updated
- Added -DHB_NO_VISIBILITY to HARFBUZZ_CFLAGS in Awt2DLibraries.gmk to avoid build issues on linux and macos targets.
- GPOS.hh moved to Layout to Layout/GPOS to match upstream changes.
- hb-ot-color-* files moved to OT/Color to match upstream changes.
- 41 newly added, 8 deleted and 224 modified files (src + harfbuzz.md).

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

Commit messages:
 - updated harfbuzz.md
 - newly added files
 - modified files
 - deleted files

Changes: https://git.openjdk.org/jdk/pull/12913/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12913&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301998
  Stats: 41531 lines in 271 files changed: 24473 ins; 11216 del; 5842 mod
  Patch: https://git.openjdk.org/jdk/pull/12913.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12913/head:pull/12913

PR: https://git.openjdk.org/jdk/pull/12913