Loki: Add in code documentation for methods and identify todos (grafana#77314)

* Loki: Add in code documentation for methods and identify todos

* Fix incorrect merge

* Fix incorrect merge

* Fix incorrect merge

* Update public/app/plugins/datasource/loki/datasource.ts

Co-authored-by: Matias Chomicki <[email protected]>

* Update comments to have less method

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Co-authored-by: Matias Chomicki <[email protected]>

Author: ivanahuckova