[Unity][BYOC] Fix RunCodegen pass on symbolic shape

[masahi]

BYOC tests using symbolic shapes have been broken since #14396. A BYOC function's return sinfo refers to a sym var defined inside that function. When a call to that is replaced by an opaque call_dps_packed, we cannot use func->ret_struct_info anymore since it refers to a sym var that's gone.

It's more mysterious why RunCodegen on symbolic shape had been working before 14396... Perhaps main happens to define the same-named sym var, which happens to capture the undefined variable in func->ret_struct_info. Perhaps that is exactly what #14396 prevents.

The failing cutlass test is now working but it is not tested on CI. Cublas tests will be added in #14291 which run on CI. We should also consider enabling cutlass tests on CI.

@sunggg @vinx13 @psrivas2 @Hzfengsy

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• cc @billishyahao, @quic-sanirudh _{See #10317 for details}

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