perf: move heavy queries to prepared statements

[ItzDerock]

I noticed that many of the feed queries end up being huge SQL statements -- nearly 4,600 characters for the main feed query. Every time someone visited the site, hit the feed API, etc, this query would be re-sent to the postgres server and the server would have to re-parse the query, re-plan and re-analyze the query, re-build the query tree, and execute.

From the postgres docs:

Prepared statements potentially have the largest performance advantage when a single session is being used to execute a large number of similar statements. The performance difference will be particularly significant if the statements are complex to plan or rewrite, e.g., if the query involves a join of many tables or requires the application of several rules.

and I'd say that definitely applies to the feed queries which have multiple subqueries, joins, etc etc.

This PR addresses this by moving all feed queries and a few other longish queries into prepared statements. I did some very preliminary testing with this, and it all seemed to work fine, but I'd recommend running some more extensive testing before pushing to prod.

[face-hh]

Hey! Thanks for the contribution - we will look over it soon.

Are the nix files required? If not, could you remove them from the PR?

[ItzDerock]

Yeah I can remove those, the nix files are for a dev environment. I think I also may have left a stray console.log somewhere, will clean that up too.

[xyzeva]

hey! any updates?

[ItzDerock]

Currently away from my computer, but you all should have push perms on this PR so feel free to checkout, delete nix files, and push.

The GitHub Mobile app doesn't let me delete files, and I don't have my signing key set up on phone.

[ItzDerock]

@xyzeva / @face-hh the extra files should be removed, PR should be good to go.

[face-hh]

I'll check this tomorrow

[face-hh]

Hey, sorry for not checking it out yesterday.

This pull request has some conflicts on api/comment and api/feed. Could you @ me whenever you resolve them?