Refactor `TimeLayerSiderPanel` to function component

[mholthausen]

Description

This refactors the TimeLayerSiderPanel to a function component. The property map will be removed, as it was neither needed nor used.

Related issues or pull requests

Pull request type

• [x] Bugfix
• [ ] Feature
• [ ] Dependency updates
• [ ] Code style update (formatting, renaming)
• [x] Refactoring
• [ ] Build related changes
• [ ] Documentation content changes
• [ ] Other (please describe)

Do you introduce a breaking change?

• [x] Yes
• [ ] No

Checklist

• [x] I understand and agree that the changes in this PR will be licensed under the BSD-2-Clause.
• [x] I have followed the guidelines for contributing.
• [x] The proposed change fits to the content of the Code of Conduct.
• [x] I have added or updated tests and documentation, and the test suite passes (run npm test locally).
• [ ] I have added a screenshot/screencast to illustrate the visual output of my update.