Enable pyupgrade, add Grid repr, and other changes

[VeckoTheGecko]

• Upgrade to f-strings (wasn't done automatically by pyupgrade)
• Enable pyupgrade
• Remove code targeting Python 2
• Add repr for Grid class (and some tooling for testing reprs)
• Type annotations and typos

related to #1620 and #1693

Breaking changes

• Field.from_netcdf() no longer supports full_load as a parameter. This was a legacy parameter from before version 2 of Parcels and hasn't been documented in tutorials and docstrings since. Use deferred_load instead.

[codecov]

Codecov Report

Attention: Patch coverage is 16.66667% with 55 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
parcels/compilation/codegenerator.py	0.00%	16 Missing ⚠️
parcels/kernel.py	0.00%	10 Missing ⚠️
parcels/grid.py	0.00%	6 Missing ⚠️
parcels/tools/converters.py	0.00%	5 Missing ⚠️
parcels/fieldset.py	0.00%	4 Missing ⚠️
parcels/field.py	57.14%	2 Missing and 1 partial ⚠️
parcels/particle.py	25.00%	3 Missing ⚠️
parcels/particlefile.py	0.00%	2 Missing ⚠️
parcels/compilation/codecompiler.py	0.00%	1 Missing ⚠️
parcels/interaction/interactionkernel.py	0.00%	1 Missing ⚠️
... and 4 more

❗ There is a different number of reports uploaded between BASE (3a7494d) and HEAD (0296e1c). Click for more details.

HEAD has 7 uploads less than BASE

Flag	BASE (3a7494d)	HEAD (0296e1c)
unit-tests	4	0
integration-tests	3	0

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1680       +/-   ##
===========================================
- Coverage   81.18%   15.82%   -65.36%     
===========================================
  Files          72       43       -29     
  Lines       13256     7872     -5384     
  Branches      127      129        +2     
===========================================
- Hits        10762     1246     -9516     
- Misses       2457     6497     +4040     
- Partials       37      129       +92     

Flag	Coverage Δ
integration-tests	?
mypy	15.82% <16.66%> (+0.17%)	⬆️
unit-tests	?

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

Files with missing lines	Coverage Δ
parcels/_typing.py	96.66% <100.00%> (-3.34%)	⬇️
parcels/tools/_helpers.py	55.00% <100.00%> (-40.00%)	⬇️
parcels/tools/exampledata_utils.py	88.50% <100.00%> (-11.50%)	⬇️
parcels/tools/interpolation_utils.py	77.34% <100.00%> (-14.00%)	⬇️
parcels/compilation/codecompiler.py	6.83% <0.00%> (-84.60%)	⬇️
parcels/interaction/interactionkernel.py	21.21% <0.00%> (-55.80%)	⬇️
parcels/particleset.py	6.37% <0.00%> (-60.57%)	⬇️
parcels/rng.py	21.48% <0.00%> (-70.32%)	⬇️
parcels/tools/global_statics.py	31.81% <0.00%> (-51.52%)	⬇️
parcels/tools/timer.py	8.92% <0.00%> (-75.00%)	⬇️
... and 8 more

... and 48 files with indirect coverage changes