test: move greenprint and redprint functions to shared_lib.sh

Since we're sharing functions between test scripts, move greenprint(),
the most rewritten function in the history of the project, to
shared_lib.sh and source it everywhere.

test/cases/filesystem.sh

@@ -12,11 +12,6 @@ source /etc/os-release
 
 source /usr/libexec/tests/osbuild-composer/shared_lib.sh
 
-# Colorful output.
-function greenprint {
-    echo -e "\033[1;32m[$(date -Isecond)] ${1}\033[0m"
-}
-
 TEST_UUID=$(uuidgen)
 IMAGE_KEY="osbuild-composer-test-${TEST_UUID}"