Migrate configuration store to Pinia

[davelopez]

We need to do this sooner or later and I hope it will simplify or remove other issues in the future (like #16420 (comment))

See individual commits for more information, in summary:

• Migrate the Galaxy configuration Vuex store to Pinia
• Adapt the config composable to use the new Pinia store
• Drop the ConfigProvider in all components and use the composable instead
• Adapt relevant client tests to use Pinia and mock configuration API calls with mockFetcher

TODO

• Drop ConfigProvider
• Add configuration model to the API schema

How to test the changes?

• This is a refactoring of components with existing test coverage.

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[davelopez]

I think this is ready to be reviewed. I will follow up with the API schema enhancements in a different PR.

[davelopez]

Thank you so much @ElectronicBlueberry!