Externalize pypi map into a ro sqlite database

[airportyh]

Why?

Having to load in the large maps within pypi_map.gen.go file into memory at start is causing upm 0.2 - 0.3 seconds.
Context: https://github.com/replit/goval/pull/9988#issuecomment-1646262367
We can eliminate this slowdown by externalizing this data into a lightweight database.

Changes

1. Replaced gen_code.go with gen_db.go which generates a read-only sqlite database containing the equivalent data
2. created pypi_map.go - convenience wrapper for accessing the db's data
3. updated all accesses to any map in pypi_map.gen.go to accessing the same data using pypi_map.go instead
4. updated upm.nix to generate the db and setup an env var to point to its location for pypi_map.go to access it

Operations to be re-tested:

• python search
• python package guess

Performance enhancement should affect all languages and all operations.

Testing

1. nix build
2. mkdir play; cd play
3. create main.py containing:

import yaml
import requests
import flask

4. time ../result/bin/upm lock
5. time ../result/bin/upm guess -f

If you compare to the version in head, should see a sizable decrease in run time. In my local testing I saw ~200x for lock (when no op) and ~60x for guess.

Also, re-test upm guess -f -l python and upm search -l python <query> to make sure those still work.

[ryantm]

$ tree result
result
├── bin
│   ├── gen_pypi_map
│   └── upm
└── pypi_map.sqlite

Do we need the bin/gen_pypi_map file? It is pretty big.

[airportyh]

Do we need the bin/gen_pypi_map file? It is pretty big.

That's only used for dev. I can look into getting rid of it. Probably a config to the buildGoModule call.