ENH: Better error message on fpath

[larsoner]

Improves the error message from:

RuntimeError: Found more than one matching data file for the requested recording.
Cannot proceed due to the ambiguity. This is likely a problem with your BIDS dataset.
Please run the BIDS validator on your data.

to

RuntimeError: Found more than one matching data file for the requested recording. While searching:
    BIDSPath(
    root: /home/larsoner/mne_data/ds004024
    datatype: eeg
    basename: sub-CON001_ses-async14ms_task-rest)
Found 4 paths:
    /home/larsoner/mne_data/ds004024/sub-CON001/ses-async14ms/eeg/sub-CON001_ses-async14ms_task-rest_run-01_eeg.vhdr
    /home/larsoner/mne_data/ds004024/sub-CON001/ses-async14ms/eeg/sub-CON001_ses-async14ms_task-rest_run-02_eeg.vhdr
    /home/larsoner/mne_data/ds004024/sub-CON001/ses-async14ms/eeg/sub-CON001_ses-async14ms_task-rest_run-03_eeg.vhdr
    /home/larsoner/mne_data/ds004024/sub-CON001/ses-async14ms/eeg/sub-CON001_ses-async14ms_task-rest_run-04_eeg.vhdr
Cannot proceed due to the ambiguity. This is likely a problem with your BIDS dataset.
Please run the BIDS validator on your data.

which allowed me to see the problem/ambiguity easily.

[codecov]

Codecov Report

Merging #1097 (97e71f8) into main (62fbde8) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #1097   +/-   ##
=======================================
  Coverage   95.21%   95.21%           
=======================================
  Files          24       24           
  Lines        3867     3869    +2     
=======================================
+ Hits         3682     3684    +2     
  Misses        185      185           

Impacted Files	Coverage Δ
mne_bids/path.py	97.62% <100.00%> (+<0.01%)	⬆️

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[sappelhoff]

Nice, I love these small improvements. Thanks!