PERF: Use optimized take path for non-nanosecond datetime64/timedelta64

[jbrockmendel]

Summary

• The take dispatch dictionaries only had entries for datetime64[ns] and timedelta64[ns]. Any other resolution fell through to the slow _take_nd_object fallback instead of the optimized Cython take_*_int64_int64 functions.
• Fix _get_take_nd_function_cached and take_2d_multi to route dtype.kind in "mM" to the int64 wrapper for all resolutions.
• Fix _view_wrapper fill value handling to use .view("i8") instead of hardcoding ns resolution (resolves existing FIXME).

~4.6x faster for 1d take, ~1.5x for 2d take on non-ns datetime64/timedelta64 arrays.

Test plan

• New tests verify _get_take_nd_function_cached returns optimized function for non-ns resolutions (1d/2d, datetime64/timedelta64, us/ms/s)
• New correctness tests for 1d and 2d take with fill on non-ns arrays
• Existing take, datetimelike, indexing, and reindex tests all pass

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