In this change I'm keeping both old and new implementations of the list
files endpoint, which is implemented in FileInfoJson. This is gated by a
config whose default is false (uses the old implementation).
Both implementations will be kept temporarily. The new implementation
should soon become the default and the old will be deprecated.
I also added a config to RevisionDiffIT to run all the tests with the
new config. Three tests are ignored with the new cache config enabled
with assume().that(useNewDiffCache).isFalse().
I will fix these tests in a follow up change.
Change-Id: Ia3a97599f800a808fa82962b5f2371f9f6264827
5a2fc8289d