[gTest] Add more test coverage for Batchnorm Backward

[xinlipn]

More test cases added for better coverage. Here's the summary

1. N C H W: 128 256 14 14 Covers: backward_spatial_single.cpp: variant == 3 and variant == 1 (2nd) 128 256 14 14.txt

2. N C H W: 128 256 16 16 Covers: backward_spatial_single.cpp: variant == 3 128 256 16 16.txt

3. N C H W: 768 1 14 14 Covers: backward_spatial_multiple.cpp: variant == 2 670 1 224 224.txt Three tests failed

Notes: For the same reason as this PR3444

1. backward_spatial_single.cpp will never reach this snippet, therefore, variant will never be 2 https://github.com/ROCm/MIOpen/blob/70c28bc39cefda94b8b87352240173e81122ea39/src/solver/batchnorm/backward_spatial_single.cpp#L185-L194

2. backward_spatial_multiple.cpp will never reach the following two snippets https://github.com/ROCm/MIOpen/blob/70c28bc39cefda94b8b87352240173e81122ea39/src/solver/batchnorm/backward_spatial_multiple.cpp#L128-L180 https://github.com/ROCm/MIOpen/blob/70c28bc39cefda94b8b87352240173e81122ea39/src/solver/batchnorm/backward_spatial_multiple.cpp#L195-L202

[xinlipn]

Previously failed test case MI200 due to tolerance issue has passed

{670, 1, 224, 224, miopenBNSpatial, miopen::batchnorm::Direction::Backward, 0, 1}};

No tolerance issue.txt

[bghimireamd]

changes from this branch was merged into https://github.com/ROCm/MIOpen/pull/3399

[BradPepersAMD]

MIOpen is moving to the new monorepo setup and all older unmerged PR's are being closed. Please re-open this as part of the new repo if these changes are still needed.