refactor(monitoring): remove hardcoded tool paths

Remove SAPCONTROL_PATH and HDBSQL_PATH variables from configuration.
Update scripts to rely on the system PATH environment variable when
executing as the <sid>adm user. Remove redundant existence checks for
these commands.

hana_lib.sh

@@ -89,7 +89,7 @@ execute_hana_sql() {
     local sql_query="$1"
     local output
     
-    output=$(su - "$HANA_USER" -c "$HDBSQL_PATH -U $HANA_USER_KEY -j -a -x \"$sql_query\"" 2>&1)
+    output=$(su - "$HANA_USER" -c "hdbsql -U $HANA_USER_KEY -j -a -x \"$sql_query\"" 2>&1)
     local sql_status=$?
     
     if [ $sql_status -ne 0 ]; then