Add -v/--verbose flag to verdi devel tests

[sphuber]

Fixes #1805

This flag will cause the unittest test runner to print the class
and function name of each test that is run. This is useful when
tracking down a particular test that is failing or is causing the
tests to hang.

[codecov-io]

Codecov Report

Merging #1807 into develop will decrease coverage by 0.02%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop    #1807      +/-   ##
===========================================
- Coverage    66.61%   66.58%   -0.03%     
===========================================
  Files          314      314              
  Lines        32344    32346       +2     
===========================================
- Hits         21545    21538       -7     
- Misses       10799    10808       +9

Impacted Files	Coverage Δ
aiida/cmdline/params/options/__init__.py	100% <100%> (ø)	⬆️
aiida/cmdline/commands/cmd_devel.py	79.35% <100%> (+0.13%)	⬆️
aiida/backends/djsite/globalsettings.py	81.57% <0%> (-5.27%)	⬇️
aiida/backends/djsite/db/models.py	75.34% <0%> (-0.89%)	⬇️

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