Report offending input in register error messages

[jaewonyun1234]

Same as #1094, applied to base_register.py.

Nine messages updated: __init__, _init_kwargs, find_indices,
from_coordinates, four in _validate_layout, and define_detuning_map.

Also fixed a missing space that printed as Label length (3) does notmatch number of coordinates (2).

I left "Cannot create a Register with an empty qubit dictionary." alone. The
dictionary is empty, so there's nothing to print.

One thing I noticed: trap_coords[trap_id] on line 229 isn't bounds checked, so
a bad trap id gives a numpy error instead of a Pulser one.

>>> Register(qubits, layout=layout, trap_ids=(0, 99))
IndexError: index 99 is out of bounds for axis 0 with size 4

RegisterLayout.define_register catches this but the Register constructor
skips that check. I didn't fix it here since it changes behaviour, not wording.

Partially addresses #1057.

[jaewonyun1234]

Hi @a-corni ready for review whenever you have time.

For the trap_ids bounds check I mentioned at the bottom — happy to fold a fix
into this PR, or open it as a separate issue. Whichever you prefer.