Update release notes to 11.0.20.1+1
Add backport of JDK-8312489 already upstream in 11.0.22 (see OPENJDK-2095)
Add backport of JDK-8243210 already upstream in 11.0.21 (see RH2229269)
Update openjdk_news script to specify subdirectory last
Add missing discover_trees script required by openjdk_news
Resolves: rhbz#2236590
