Speed up FrameFileTest, SuperSorterTest.

[gianm]

These are two heavily parameterized tests that, together, account for about 60% of runtime in the druid-processing test suite.

FrameFileTest changes:

1. Cache frame files in a static, rather than building the frame file
   for each parameterization of the test.

2. Adjust TestArrayCursorFactory to cache the signature, rather than
   re-creating it on each call to getColumnCapabilities.

SuperSorterTest changes:

1. Dramatically reduce the number of tests that run with
   "maxRowsPerFrame" = 1. These are particularly slow due to writing so
   many small files. Some still run, since it's useful to test edge cases,
   but much fewer than before.

2. Reduce the "maxActiveProcessors" axis of the test from [1, 2, 4] to
   [1, 3]. The aim is to reduce the number of cases while still getting
   good coverage of the feature.

3. Reduce the "maxChannelsPerProcessor" axis of the test from [2, 3, 8]
   to [2, 7]. The aim is to reduce the number of cases while still getting
   good coverage of the feature.

4. Use in-memory input channels rather than file channels.

5. Defer formatting of assertion failure messages until they are needed.

6. Cache the cursor factory and its signature in a static.

7. Cache sorted test rows (used for verification) in a static.

[gianm]

CI just finished, the change appears to chop an hour off the processing unit test time.

[kfaraz]

Need to backport this to allow backporting #17088.
Otherwise, there are some merge conflicts.