Support other APIs and metric types using a new providers interface

[abhidg]

This PR adds a providers interface that replaces the current CI_api_query and CI_api_interface classes. The advantage of the new approach is that it allows further customisation of the provider rather than customising the URL; this is useful to support providers that might need us to interface directly with a databases or with HTTP APIs requiring authentication. New types (Timeseries) have been added to support not just carbon intensity, but any other type of forecast timeseries with customizable units.

Other changes:

• Added type hinting throughout
• Using Exceptions for error handling (cats.exceptions) which allows us to consolidate error handling in one place (main()) as well as providing type based checking
• Added --save-plot to save plots to file

Remaining refactor would be to move configuration parsing and error handling out of cats/cli.py, this will be done in a subsequent PR.

[codecov]

Codecov Report

❌ Patch coverage is 84.12698% with 50 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.83%. Comparing base (f623ba4) to head (6d6402d).
⚠️ Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
cats/plotting.py	19.44%	29 Missing ⚠️
cats/cli.py	81.13%	10 Missing ⚠️
tests/test_configure.py	36.36%	7 Missing ⚠️
cats/providers/uk_carbonintensity.py	93.02%	3 Missing ⚠️
cats/providers/base.py	97.22%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #196      +/-   ##
==========================================
+ Coverage   87.17%   87.83%   +0.65%     
==========================================
  Files          20       22       +2     
  Lines        1092     1192     +100     
==========================================
+ Hits          952     1047      +95     
- Misses        140      145       +5     

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[andreww]

Happy overall. Probably worth briefly thinking about the location / time aspect of the API. Does this also close some further issues (e.g. renaming CI modules)? If so worth making sure we capture these.

[andreww]

We should probably create space in the documentation for how to do this. Happy to write it as I work out how (probably via wattnet) or you can put a stub in place as part of this PR.

[andreww]

The readthedocs and cluster-tests failures look like they linked. Both report not being able to import "cats.providers", but I cannot immediately reproduce locally.