Fix unit test failures on CPU and GPU

[minjang]

We still have some testing failures on CPU and GPU. This PR tries to fix most of them. I reverted some of the changes in test_conversions.py and test_conversions.py.

TRITON_CPU_BACKEND=1 python -m pytest -s -n 16 --device cpu python/test/unit/language/test_annotations.py python/test/unit/language/test_block_pointer.py python/test/unit/language/test_compile_errors.py python/test/unit/language/test_conversions.py python/test/unit/language/test_decorator.py python/test/unit/language/test_pipeliner.py python/test/unit/language/test_random.py python/test/unit/language/test_standard.py python/test/unit/runtime/test_autotuner.py python/test/unit/runtime/test_bindings.py python/test/unit/runtime/test_cache.py python/test/unit/runtime/test_driver.py python/test/unit/runtime/test_jit.py python/test/unit/runtime/test_launch.py python/test/unit/runtime/test_subproc.py python/test/unit/test_debug_dump.py -v

TRITON_CPU_BACKEND=0 python -m pytest -s -n 16 --device cuda python/test/unit/language/test_annotations.py python/test/unit/language/test_block_pointer.py python/test/unit/language/test_compile_errors.py python/test/unit/language/test_conversions.py python/test/unit/language/test_decorator.py python/test/unit/language/test_pipeliner.py python/test/unit/language/test_random.py python/test/unit/language/test_standard.py python/test/unit/runtime/test_autotuner.py python/test/unit/runtime/test_bindings.py python/test/unit/runtime/test_cache.py python/test/unit/runtime/test_driver.py python/test/unit/runtime/test_jit.py python/test/unit/runtime/test_launch.py python/test/unit/runtime/test_subproc.py python/test/unit/test_debug_dump.py -v