dct tests: run all possible sizes in one test

dct tests: run all possible sizes in one test

Modify fdct4x4_test.cc to support all size combinations. This does not
add any new tests and in fact fails a few. There were minimal changes
made to the tests so it's not entirely surprising that some of the
larger 12 bit transforms are failing since it was initially only used
for 4x4.

In follow up patches the tests in fdct8x8_test.cc, dct16x16_test.cc and
dct32x32_test.cc will be evaluated and moved to dct_test.cc.

BUG=webm:1424

Change-Id: I72a23430f457d7fae8c91e706adc0e77c25abc8f