Restore isSameAs/isNotSameAs extension functions to AssertKExtensions.kt

These custom extensions were incorrectly removed in commit 3d649d9, causing
compilation errors in DefaultContextTest.kt and XMLContextFactoryTest.kt.

AssertK 0.28.1 does not provide isSameAs()/isNotSameAs() methods - these
were custom extensions for checking object identity (===) that are still
needed by the test suite.

Co-authored-by: bedaHovorka <bedaHovorka@users.noreply.github.com>

Author: github-actions[bot]

src/test/kotlin/cz/vutbr/fit/interlockSim/testutil/AssertKExtensions.kt

@@ -101,6 +101,30 @@ fun <T> Assert<Collection<T>>.containsAnyOf(vararg elements: T) = given { actual
 	expected("to contain any of:${show(elements.toList())} but was:${show(actual)}")
 }
 
+/**
+ * Extension function to assert that two objects are the same instance.
+ *
+ * Usage: assertThat(obj1).isSameAs(obj2)
+ */
+fun <T> Assert<T>.isSameAs(expected: T): Assert<T> = apply {
+	given { actual ->
+		if (actual === expected) return@given
+		expected("to be the same instance as:${show(expected)} but was:${show(actual)}")
+	}
+}
+
+/**
+ * Extension function to assert that two objects are not the same instance.
+ *
+ * Usage: assertThat(obj1).isNotSameAs(obj2)
+ */
+fun <T> Assert<T>.isNotSameAs(expected: T): Assert<T> = apply {
+	given { actual ->
+		if (actual !== expected) return@given
+		expected("to not be the same instance as:${show(expected)}")
+	}
+}
+
 /**
  * Extension function to assert that a block of code executes without throwing an exception.
  *