test: new weldr client compatibility for test scripts

- Handle the array responses from the new weldr-client (>= 35.6).
- Move the `get_build_info` function to shared_libs.sh to source and
  reuse in multiple places.

test/cases/ostree-simplified-installer.sh

@@ -13,14 +13,7 @@ function greenprint {
     echo -e "\033[1;32m[$(date -Isecond)] ${1}\033[0m"
 }
 
-function get_build_info() {
-    key="$1"
-    fname="$2"
-    if rpm -q --quiet weldr-client; then
-        key=".body${key}"
-    fi
-    jq -r "${key}" "${fname}"
-}
+source /usr/libexec/tests/osbuild-composer/shared_lib.sh
 
 # Start firewalld
 sudo systemctl enable --now firewalld