tools: add report_v_module_folders_without_tests.v . Use it to discover other modules without _test.v files. Add simple ones, to ensure CI can find more breakage on future wide changes to vlib/

vlib/hash/hash_compiles_test.v

@@ -0,0 +1,5 @@
+import hash
+
+fn test_hash_compiles() {
+	assert hash.sum64_string('abc', 5).hex_full() == 'ce2703347d216491'
+}