Refactor framework

[manchester-jhellier]

1. DataOrder is densely coupled to things in framework.py (especially DataContainer). To alleviate this, {ImageGeometry,AcquisitionGeometry}.{CHANNEL,VERTICAL,...} is replaced with with labels.Enum (fixes DataOrder is a problem and should be destroyed #1691)
2. break framework.py into smaller pieces (fixes Break framework.py into smaller pieces #1686)

@casperdcl checklist

• rebase/merge
• rework labels
  • use StrEnum
  • combine AcquisitionTypes & AcquisitionDimensions into AcquisitionType(enum.Flag)
  • better OOP for {get,check}_order_for_engine()
  • discuss/debate naming (e.g. FillTypes -> FillType etc.)

tests

• CIL CI
• SIRF CI?

review checklist

• I have performed a self-review of my code
• I have added docstrings in line with the guidance in the developer guide
• I have implemented unit tests that cover any new or modified functionality
• CHANGELOG.md has been updated with any functionality change
• add Josh & Nick to NOTICE.txt
• Request review from all relevant developers
• Change pull request label to 'Waiting for review'
• Check documentation renders correctly
• check notebooks
  • binder
  • colab @hrobarts
  • demos/1_Introduction @hrobarts
  • demos/2_Iterative @MargaretDuff
  • demos/3_Multichannel @casperdcl
  • demos/appendix.ipynb
  • misc

Contribution Notes

Please read and adhere to the developer guide and local patterns and conventions.

• The content of this Pull Request (the Contribution) is intentionally submitted for inclusion in CIL (the Work) under the terms and conditions of the Apache-2.0 License.
• I confirm that the contribution does not violate any intellectual property rights of third parties

[manchester-jhellier]

Added a whole load of new commits to break framework.py into smaller files. Largest file is now only ~1900 lines long!

[manchester-jhellier]

SIRF tests run using Docker, and those have been amended so they pass (turned out there was a lot less stuff being imported from CIL than I'd thought).

[hrobarts]

I checked the documentation and it looks fine. I added the labels separately but can remove them if we don't want them in the user-facing docs.
I also re-checked some demo notebooks (Introduction, binder, colab, a couple in misc) and they all seem to be fine apart from the warnings we know about for v 24 TomographicImaging/CIL-Demos#155 .
Happy to approve :)

[MargaretDuff]

Have run a few of the iterative (folder 2) demo notebooks and all is fine there

[gfardell]

The documentation is a bit odd. The class name is strange, and the white space between the attributes. I guess it's useful to have the classes in the documentation, but I'm not sure the best way to show the attributes and values people can use/get.

Does anyone have any ideas/examples?

[casperdcl]

Congratulations @manchester-jhellier you are now 4th in the list!