Initial upgrade to "Code QA Sprint" standards

[pp-mo]

Updated pre-commit config, to be compared with recommendations in "Scitools Code Quality Bonanza" project

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.60%. Comparing base (d00965d) to head (d6d581e).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #564   +/-   ##
=======================================
  Coverage   89.60%   89.60%           
=======================================
  Files           8        8           
  Lines        2473     2473           
  Branches      420      420           
=======================================
  Hits         2216     2216           
  Misses        159      159           
  Partials       98       98           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[pp-mo]

TODO

Heads-up for what isn't here, to be addressed next (or ruled out-of-scope for the Code-QA sprint project) :

• additional disabled numpydocs-validation checks : remove some, where straightforward, with matching source changes
• temporary disables in ./.ruff.toml : see if we can target some of these
• still using mypy "strict=false"
  (but that one's probably too much work to fix at this point)

[pp-mo]

Fixed up to a point, probably a reasonable starting position.
The remaining numpydocs checks which we'd like to enable are the following :

$ pre-commit run numpydoc-validation --all-files | grep -oE "\| *[[:alpha:]]+[[:digit:]]+ *\|" | sort | uniq -c` 
     70 | GL08    |
    119 | PR01    |
     55 | RT01    |

with the meanings

check	#occurs	meaning
GL08	70	The object does not have a docstring
PR01	119	Parameters { ... } not documented
RT01	55	No Returns section found

[pp-mo]

Rebased following update for dependabot changes.
I think rebased is easier to look at.
Anyway, you should consider the last commit separately @ukmo-ccbunney (!)