Add function to make a snapshot of current test project

This will allow checking current state of test project and try
to work with it directly.

^KT-45745 In Progress

libraries/tools/kotlin-gradle-plugin-integration-tests/Readme.md

@@ -88,7 +88,7 @@ add a new assertion, add as a reviewer someone from Kotlin build tools team.
 
 ##### Additional test helpers
 
-Whenever you need to test combination of different JDKs and Gradle versions - you could use `@GradleWithJdkTest` instead of `@GradleTest`. 
+- Whenever you need to test combination of different JDKs and Gradle versions - you could use `@GradleWithJdkTest` instead of `@GradleTest`. 
 Then test method will receive requires JDKs as a second parameter:
 ```kotlin
 @JdkVersions(version = [JavaVersion.VERSION_11, JavaVersion.VERSION_17])
@@ -103,6 +103,8 @@ fun someTest(
 }
 ```
 
+- If you want to copy current state of the test project and play with it separately - you could use `makeSnapshotTo(destinationPath)` function.
+
 ##### Common test fixes
 
 Test infrastructure adds following common fixes to all test projects: