feat: add authMethod to kratix chart

[Knapsack44]

I seem to have messed something up due to the fact that my email address was missing from the commit. This meant that the CLA could not accept correctly. Hopefully everything should be fine now.

Original PR:
This PR will add the possibility to define the authMethod for the Kratix helm chart. If no value is defined, the value is automatically set to basicAuth. With my change, this will also be explicit visible.

[ChunyiLyu]

@Knapsack44 Thanks again for contributing.

We support two different StateStore that has different defaults. For our GitStateStore, default authentication method is basicAuth, for BucketStateStore, default is accessKey. The team think it's better to leave defaulting to the controller as it's already been done in:
https://github.com/syntasso/kratix/blob/main/api/v1alpha1/bucketstatestore_types.go#L40
https://github.com/syntasso/kratix/blob/main/api/v1alpha1/gitstatestore_types.go#L44

There's definitely value in allowing setting authMethod for the chart. May I suggest modify the PR to define the authMethod and remove the part about setting default?