[pallas] Improve error and debugging messages with source locations
Document the `name` argument to `pallas_call` and supplement it with source location information for the kernel function.
Pass all this as the `name_and_src_info` parameter to the `pallas_call_p` primitive.
Added some more information to the `if debug` prints.
Set the MLIR module names so that the debug dumps are named properly.
I changed `import pallas.core as pl_core` to `... as pallas_core` for consistency, in a couple of modules.
PiperOrigin-RevId: 659506675
