refactor(strhelpers): extract shared strReplaceAll helper (#7711)

Co-authored-by: philmoz <philmoz@users.noreply.github.com>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

radio/src/tests/strhelpers.cpp

@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) EdgeTX
+ *
+ * Based on code named
+ *   opentx - https://github.com/opentx/opentx
+ *   th9x - http://code.google.com/p/th9x
+ *   er9x - http://code.google.com/p/er9x
+ *   gruvin9x - http://code.google.com/p/gruvin9x
+ *
+ * License GPLv2: http://www.gnu.org/licenses/gpl-2.0.html
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include "gtests.h"
+#include "strhelpers.h"
+
+TEST(StrHelpers, ReplaceAllEmptyFrom)
+{
+  std::string s = "hello world";
+  strReplaceAll(s, "", "x");
+  EXPECT_EQ(s, "hello world");
+}
+
+TEST(StrHelpers, ReplaceAllEmptyTo)
+{
+  std::string s = "hello world";
+  strReplaceAll(s, "o", "");
+  EXPECT_EQ(s, "hell wrld");
+}
+
+TEST(StrHelpers, ReplaceAllNoMatch)
+{
+  std::string s = "hello world";
+  strReplaceAll(s, "xyz", "abc");
+  EXPECT_EQ(s, "hello world");
+}
+
+TEST(StrHelpers, ReplaceAllOverlappingMatches)
+{
+  std::string s = "aaaa";
+  strReplaceAll(s, "aa", "a");
+  EXPECT_EQ(s, "aa");
+}
+
+TEST(StrHelpers, ReplaceAllToContainsFrom)
+{
+  std::string s = "cat";
+  strReplaceAll(s, "cat", "concatenate");
+  EXPECT_EQ(s, "concatenate");
+}
+
+TEST(StrHelpers, ReplaceAllMultipleMatches)
+{
+  std::string s = "a,b,c,d";
+  strReplaceAll(s, ",", " - ");
+  EXPECT_EQ(s, "a - b - c - d");
+}