WIP, ENH: Nicer ProgressBar

[larsoner]

Using the snippet from 7155 on master we get:

Downloading https://github.com/mne-tools/mne-python/blob/master/README.rst (0 bytes)
[............................................................] unknown (   75 kB,    74 kB/s) |
File saved as /tmp/null.

[............................................................] 100.00% Finding flat segments /
Marking 0.01% of time points (3 segments) and 0/364 channels bad: []
[............................................................] 100.00% Fitting GeneralizingEstimator |
[............................................................] 100.00% Scoring GeneralizingEstimator |

This PR adds to / changes our code to look better:

Downloading https://github.com/mne-tools/mne-python/blob/master/README.rst (0 bytes)
unknown▕████████████████████████████████████████████████████████████▏(   75 kB,    74 kB/s) |
File saved as /tmp/null.

100.00%▕████████████████████████████████████████████████████████████▏Finding flat segments /
Marking 0.01% of time points (3 segments) and 0/364 channels bad: []
100.0%▕████████████████████████████████████████████████████████████▏Fitting GeneralizingEstimator 
100.0%▕████████████████████████████████████████████████████████████▏Scoring GeneralizingEstimator

And #7155 offloads the work to tqdm to achieve:

Downloading https://github.com/mne-tools/mne-python/blob/master/README.rst (0 bytes)
  0%|                                                                                    |  : 75.3k/0.00 [00:00<00:00,     576kB/s]
File saved as /tmp/null.

Finding flat segments
100%|███████████████████████████████████████████████████████████████████████████████| Channels : 364/364 [00:00<00:00, 2995.46it/s]
Marking 0.01% of time points (3 segments) and 0/364 channels bad
100%|██████████████████████████████████████████████████████████| Fitting GeneralizingEstimator : 106/106 [00:03<00:00,   34.89it/s]
100%|██████████████████████████████████████████████████████| Scoring GeneralizingEstimator : 11236/11236 [00:18<00:00,  598.40it/s]

Either this or #7155 should be merged before 0.20.

[drammock]

+1 for #7155 instead of this one.

[codecov]

Codecov Report

Merging #7418 into master will decrease coverage by 0.06%.
The diff coverage is 85.71%.

@@            Coverage Diff             @@
##           master    #7418      +/-   ##
==========================================
- Coverage   90.03%   89.96%   -0.07%     
==========================================
  Files         454      454              
  Lines       82228    82231       +3     
  Branches    13003    13003              
==========================================
- Hits        74030    73980      -50     
- Misses       5372     5423      +51     
- Partials     2826     2828       +2