Add flag to turn off generating a diff

[ngufra]

When the data is very large (response more than 1 MB long), the diff created using myers diff can take many minutes and hog the cpu. As we have multiple tests, this causes our test run to timeout after 1 hour.

We traced it to
val diff = generateFullDiff(actualBody.orEmpty(), contentType, expectedBody.valueAsString(), isJsonBody) in ResponseComparison.kt.

It would be valuable to use an alternate diff algorithm or disable it altogether.

Ronald Holshausen suggested we open an issue to track the change request.

[uglyog]

I've added a system property to disable the diff calculation. It can either just be turned off, or set a size threshold so small payloads will still have diffs.

[ngufra]

Many thanks for the quick implementation.

[uglyog]

4.2.7 has been released