Lazy load nwp data

[simlmx]

I recommend reviewing commit by commit and the last one is the most relevant.

• More logging and timings
• Lazy load the NWP data instead of in memory, which means we don't need as much RAM.

[peterdudfield]

Do you know why the docker tests now fail?

Otherwise it looks good

[codecov-commenter]

Codecov Report

Merging #39 (26fb2d8) into main (1e674bb) will increase coverage by 1.32%. The diff coverage is 88.88%.

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@@            Coverage Diff             @@
##             main      #39      +/-   ##
==========================================
+ Coverage   91.26%   92.59%   +1.32%     
==========================================
  Files           9       10       +1     
  Lines         252      270      +18     
==========================================
+ Hits          230      250      +20     
+ Misses         22       20       -2     

Impacted Files	Coverage Δ
pv_site_production/data/nwp_data_sources.py	69.56% <0.00%> (+1.56%)	:arrow_up:
pv_site_production/app.py	95.58% <100.00%> (+1.64%)	:arrow_up:
pv_site_production/models/psp.py	100.00% <100.00%> (ø)
pv_site_production/utils/profiling.py	100.00% <100.00%> (ø)

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