[FEA] Remove duplicated files from RAFT

[hcho3]

As noted in rapidsai/raft#229 and #3860, there are a few files that are duplicated in cuML and RAFT, such as cpp/test/prims/test_utils.h. We should locate and remove the duplicated files.

[mdemoret-nv]

Moving to the Tech Debt project. Should ensure there are no additional duplicates between cuML and RAFT.

[github-actions]

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