Add `scratch_shapes` to Pallas `pl.core_map`.
Also removed the `pl.get_global` for SparseCore because the use case is covered by `scratch_shapes`.
Also refactored `pl.kernel` to use core_map with scratch_shapes.
Also used a workaround on SC SCS due to existing memory space allocation bug.
PiperOrigin-RevId: 868830705
