Disp fills table with missing "tel" prefix, results in duplicated columns with and without tel

[maxnoe]

Describe the bug

We made a change to add a _tel between the container prefix and the field name to distinguish mono predictions from stereo predictions when loaded into the same table, code here:
https://github.com/cta-observatory/ctapipe/blob/main/ctapipe/reco/utils.py

We do this also with the per-telescope disp output, which has no stereo equivalent.

The reconstructor is also filling the table without this prefix, so the value with the tel_ prefix is added.

To Reproduce

Run the unit tests for the disp reconstructor, inspect the output:

['disp_parameter_norm',
 'disp_parameter_is_valid',
 'disp_parameter_tel_norm',
 'disp_parameter_tel_is_valid']

Expected behavior

Only have the disp_paremeter_norm and disp_parameter_is_valid columns

[Tobychev]

I think this is closed by #2440, right?

[maxnoe]

Yes, forgot to link it