migrated from Travis CI.
ICU-21434 Shorten the GitHub Action name to ICU CI only to leave more space on the dashboard.
ICU-21434 Review comments: better name, and one line turned out to be a no-op.
ICU-21434 Fix Java JDK version setting.
ICU-21434 Sort out Java version setting.
ICU-21434 Adds an entry to icu4c/source/test/depstest/dependencies.txt to fix depstest
and enable depstest.
- on a release (created from Github), publish to
<https://github.com/unicode-org/icu/packages> as
1. icu4j-for-cldr
2. utilities-for-cldr
- also fix a doc bug in DecimalFormat
- this is intended for CLDR use.
- a tag such as 'cldr/2019-09-15' will turn into a
maven version '68.1-SNAPSHOT-cldr-2019-09-15'
