Add utils::count_words and utils::trim_comment

unittest/utils/test_utils.cpp

@@ -0,0 +1,16 @@
+#include <gtest/gtest.h>
+#include <gmock/gmock.h>
+#include "utils.h"
+#include <string>
+
+using namespace LAMMPS_NS;
+using ::testing::Eq;
+
+TEST(Utils, trim_comment) {
+    auto trimmed = utils::trim_comment("some text # comment");
+    ASSERT_THAT(trimmed, Eq("some text "));
+}
+
+TEST(Utils, count_words) {
+    ASSERT_EQ(utils::count_words("some text # comment"), 2);
+}