Avoid writing extra devices when using IntanRecordingInterface with multiple electrode groups

[h-mayorquin]

As in the title.

This is after #1164 as that laid the ground-work for this.

The problem is the last time I hardcoded that we only add the IntanDevice to the first group. The other groups have a default Device and that's where the extra ones come from.

I added a test and fixed this.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.75%. Comparing base (96dfdff) to head (cce7083).
Report is 12 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1167      +/-   ##
==========================================
+ Coverage   90.69%   90.75%   +0.06%     
==========================================
  Files         129      129              
  Lines        8189     8287      +98     
==========================================
+ Hits         7427     7521      +94     
- Misses        762      766       +4     

Flag	Coverage Δ
unittests	90.75% <100.00%> (+0.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...datainterfaces/ecephys/intan/intandatainterface.py	100.00% <100.00%> (ø)

... and 3 files with indirect coverage changes