Refactor kerchunk readers to use manifest store

[TomNicholas]

Aims to refactor all the kerchunk-based readers to use ManifestStore, but to do that this PR first adds a ManifestStore.from_kerchunk_refs() method.

• [ ] Closes #xxxx
• [ ] Tests added
• [ ] Tests passing
• [ ] Full type hint coverage
• [ ] Changes are documented in docs/releases.rst
• [ ] New functions/methods are listed in api.rst
• [ ] New functionality has documentation