ENH: SPMD interface for IncrementalEmpiricalCovariance

[olegkkruglov]

Description

• Added SPMD interface for IncrementalEmpiricalCovariance
• Added example of its usage.
• Changed policy saving workflow, now queue is saved to attributes instead of policy. It is necessary because finalize_fit requires spmd_policy, but partial_fit requires data_parallel_policy on oneDAL side
• finalize_fit now uses provided queue for computations on onedal4py side.
• Contains some content from https://github.com/intel/scikit-learn-intelex/pull/1777 for test implementation

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