RFR: 8306329 : Update ICU4C to 73

[Hima Bindu Meda]

Updated ICU to v73.1. Verified build and sanity. No issues seen.

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Commit messages:
 - resolve compile error on windows
 - change file mode for rbbicst.pl
 - whitespace corrections
 - chmod to 644 for regexcst.pl
 - white space corrections
 - remove unwanted files
 - Merge branch 'master' into icu-update-73
 - update version and sha sum
 - Update CMakeLists.txt
 - Update license and remove unwanted files
 - ... and 1 more: https://git.openjdk.org/jfx/compare/e7974bc8...599b7523

Changes: https://git.openjdk.org/jfx/pull/1138/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1138&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306329
  Stats: 35594 lines in 738 files changed: 9104 ins; 2562 del; 23928 mod
  Patch: https://git.openjdk.org/jfx/pull/1138.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1138/head:pull/1138

PR: https://git.openjdk.org/jfx/pull/1138