SANS TOML V2: Polarization Options Added to User Files

[cailafinn]

Description of work

Summary of work

Allows specification of the polarisation options used in the experiment to be provided to the reduction via the user file (a file written in SANS' custom TOML format, usually one per experiment).

Fixes #38524

Further detail of work

• Created StatePolarization. An JSON-serialisable object that holds the polarisation information to be passed around as part of SANSState to algorithms and interfaces.

• Refactored the TOML parser into a base and sub-classes to support...

• Implemented SANS TOML V2 parser and schema. Upgrading to V2 means that files with the new information won't be supported by previous versions of Mantid. This is intentional. All V1 files continue to be backwards compatible, all V2 files will warn that the version is unsupported, forcing a version of Mantid to be used that can support the new polarisation options.

• Refactored some tests to remove duplication caused by the additional parser.

• Note: If required, this could be 2 PRs. The first implementing the State object and the second implementing the parsing.

To test:

1. Download this new user file, modified from the loqdemo in the training course data (you'll need that too): MaskFile_polarization.toml.zip
2. Open a nightly and open Interfaces -> SANS -> ISIS SANS
3. Attempt to select the downloaded file as the user file. It should throw.
4. Open the workbench build of this PR.
5. Repeat, it should load successfully.
6. Load the batch from the loqdemo
7. Process All
8. Find the output workspaces on the main mantid window and open the workspace history
9. Find the SANSState object
10. Copy it to clipboard, and paste it into a nice editor (I like VS code for this)
11. It'll paste in one giant line, reformat the file (install a JSON extension if necessary)
12. Check that the new polarisation information from the downloaded file is present in the JSON.

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