resolved TODO comments in db.py and library.py

[owenyu23]

Addressed TODO comments in db.py and removed TODO comments in library.py based on edits done in db.py:

• Added ORDER BY RANDOM() to get_essential_genes and get_control_guides to match the original Clojure implementation
• Cleaned up get_essential_genes
• Removed resolved TODO comments

Note that there are two TODOs (one in db.py and library.py) that still need addressing:

• get_library_info_by_gene line 114: unclear if ORDER BY is needed or if sorting should happen in library.py after fetching based on Clojure implementation
• library.py line 73: unsure if control guide percentage calculation may not be correct via the TODO comment referencing the Clojure implementation

[vineetbansal]

Thanks @owenyu23 - I don't have a clear context of what we're trying to do here (and why). If the intention is to match the python implementation to the original Clojure code, can you also include links to the relevant lines in the Clojure code?

[vineetbansal]

@owenyu23 - let's move development to the fork of this repo at https://github.com/vineetbansal/guidescanpy. I've sent you an invite. That way at least we have the assurance of the CI working while we're making changes.

Can you retarget any pending PRs to that fork instead? At some point we can do a merge to this repo, with or without the CI working here.