Apply ShutterCount Normalisation Correction when ShutterCounts Available

[JackEAllen]

Issue

Closes #2095

Description

Add a description of the changes made.

• Load ShutterCount Files into Spectrum Viewer if available.
• Only apply ShutterCount correction if bool propagated from view (currently not fully integrated)
• Apply ShutterCount correction to normalisation using only first value, but written such that more values can be used later on should requirements change.

Testing

Describe the tests that were used to verify your changes.

• Manually tested through hard coding normalise parameter in get_spectrum to True and adding log statements
• Visual inspection of how spectrum differed based on whether ShutterCount correction has been applied or not.
• Unit tests pass

Acceptance Criteria

How should the reviewer test your changes?

• Unit tests pass
• Through adding additional logs and viewing spectrum, hard coding get_spectrum normalise param to "True" applies ShutterCount correction

Documentation

How have you changed the documentation to reflect your changes? All changes should be noted in the appropriate file in docs/release_notes

docs/release_notes/next/feature-2095-apply_shuttercounts_normalisation

[coveralls]

coverage: 73.019% (+0.06%) from 72.96%
when pulling 10749f1 on 2095_shuttercount_correction
into 86644da on main.

[samtygier-stfc]

Code looks good. I have tested with a few extra print statements to see the normalisation happening.