Reduce complex GEMM pre_checkin tests

[leekillough]

This reduces the number of pre_checkin complex GEMM tests, by reducing the number of combinations of (alpha,alphai) and (beta,betai).

 ./rocblas-test  --gtest_filter=pre_checkin/gemm_strided_batched*

The runtime of the tests on a Vega 20 are reduced from:

[----------] Global test environment tear-down
[==========] 26945 tests from 2 test cases ran. (11615163 ms total)
[  PASSED  ] 26945 tests.

real    194m15.733s
user    178m29.709s
sys     14m23.518s

To:

[----------] Global test environment tear-down
[==========] 21585 tests from 2 test cases ran. (7257974 ms total)
[  PASSED  ] 21585 tests.

real    121m32.824s
user    111m35.696s
sys     9m3.093s

Combined with the BLIS changes (#621), this should lower the time it takes to run pre_checkin CI tests.

[zaliu]

LGTM

[amcamd]

LGTM