Simplified & made more robust maintenance helper script for "-O gen-C++" testing

src/script_opt/CPP/maint/find-test-files.sh

@@ -1,10 +1,9 @@
 #! /bin/sh
 
 find ../testing/btest -type f |
-    grep -E -v 'Baseline|\.tmp|__load__' |
-    grep -E '\.(zeek|test)$' |
-    sort |
+    xargs grep -E -l '@TEST' |
     xargs grep -E -l '^[ 	]*(event|print)' |
     xargs grep -E -c 'REQUIRES.*CPP.*((!=.*1)|(==.*0))' |
     grep ':0$' |
-    sed 's,:0,,'
+    sed 's,:0,,' |
+    sort