mx-cookie-test (I presume you mean this one and not mx-test-cookie) is a cookie we temporarily set to verify whether we have access to cookies. This helps us determine whether we need to warn the user that he/she needs to enable them, as Mendix heavily relies on cookies to function.
I believe _GA cookies are for Google Analytics? They shouldn't be needed for a non-customized Mendix app to run.
Is this still valid? I found the following after a quick analysis.
Hybrid /false
DeviceType /Desktop
xasid /0.5243b142-9bc5-4aa5-ba06-5997f4b94e67
XASSESSIONID /44b3a5b1-0016-4e4f-9fb0-98d4c3554915
originURI /login.html