Add 20B GPTBigCode Tiny Model

[fabianlim]

Add the 20G GPTBigCode tiny model and check the tests. This PR requires foundation-model-stack#431

Running this command passes

FMS_TEST_SHAPES_FAILURE_THRESHOLD=0.3 pytest -vv -s aiu-fms-testing-utils/tests/models/test_decoders.py


====================================================================== fixture duration top ======================================================================
total          name               num avg            min
0:00:00.000840        grand total  40 0:00:00.000011 0:00:00.000008
===================================================================== test call duration top =====================================================================
total          name               num avg            min
0:16:53.605807 test_common_shapes   8 0:01:11.382130 0:00:52.707010
0:16:53.605807        grand total   8 0:01:11.382130 0:00:52.707010
==================================================================== test setup duration top =====================================================================
total          name               num avg            min
0:00:00.002235        grand total   8 0:00:00.000255 0:00:00.000181
=================================================================== test teardown duration top ===================================================================
total          name               num avg            min
0:00:00.006282 test_common_shapes   8 0:00:00.000612 0:00:00.000253
0:00:00.006282        grand total   8 0:00:00.000612 0:00:00.000253
================================================================= 8 passed in 1013.64s (0:16:53) =================================================================