[CK_BUILDER] Add inline string diff for tests (#3067)

Adds new testing functionality: an inline diff for string comparison.

Example usage:

EXPECT_THAT("Actual string", ck_tile::test::StringEqWithDiff("Expected string"));

Failure message:

Value of: "Actual string"
Expected: "Expected string"
Actual: "Actual string" (of type char [14]),
Diff: "[Expe|A]ct[ed|ual] string"

The inline-diff function uses the Wagner-Fischer algorithm to find the minimum edit distance and generate diff markers, which has O(N^2) complexity. It has optional color codes that are enabled with the matcher.

experimental/builder/test/testing_utils.hpp

@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2018-2025, Advanced Micro Devices, Inc. All rights reserved.
+
+#include <gtest/gtest.h>
+#include <gmock/gmock.h>
+#include <string>
+#include <sstream>
+
+namespace ck_tile::test {
+
+static bool isTerminalOutput() { return isatty(fileno(stdout)) || isatty(fileno(stderr)); }
+
+// Returns a string highlighting differences between actual and expected.
+// Differences are enclosed in brackets with actual and expected parts separated by '|'.
+std::string inlineDiff(const std::string& actual,
+                       const std::string& expected,
+                       bool use_color = isTerminalOutput());
+
+// A convenience alias for inlineDiff to improve readability in test assertions.
+// Note that the function has O(n^2) complexity both in compute and in memory - do not use for very
+// long strings
+std::string formatInlineDiff(const std::string& actual, const std::string& expected);
+
+// Gmock matcher for string equality with inline diff output on failure
+class StringEqWithDiffMatcher : public ::testing::MatcherInterface<std::string>
+{
+    public:
+    explicit StringEqWithDiffMatcher(const std::string& expected);
+
+    bool MatchAndExplain(std::string actual,
+                         ::testing::MatchResultListener* listener) const override;
+
+    void DescribeTo(std::ostream* os) const override;
+    void DescribeNegationTo(std::ostream* os) const override;
+
+    private:
+    std::string expected_;
+};
+
+// Factory function for the StringEqWithDiff matcher
+::testing::Matcher<std::string> StringEqWithDiff(const std::string& expected);
+
+} // namespace ck_tile::test