Measure unit test coverage

[nfx]

Pytest drops coverage as a SQLite database. Query: select * from arc left join file on arc.file_id = file.id left join context on arc.context_id = context.id;

in go, we can either subprocess https://go.dev/doc/build-cover or parsed https://github.com/golang/go/blob/0104a31b8fbcbe52728a08867b26415d282c35d2/src/cmd/cover/html.go#L85-L100

go cover profile can also be used to build a treemap: https://github.com/golang/go/blob/0104a31b8fbcbe52728a08867b26415d282c35d2/src/cmd/cover/html.go#L85-L100