We upgraded our minimum Go version to 1.21 in commit
57ac9c2189458a7f0e63c2e9cac8334694a3d545. We can now replace our
`utils.Min` and `utils.Max` functions with the built-in `min` and `max`.
Reference: https://go.dev/ref/spec#Min_and_max
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>
We've been sometimes using lo and sometimes using my slices package, and we need to pick one
for consistency. Lo is more extensive and better maintained so we're going with that.
My slices package was a superset of go's own slices package so in some places I've just used
the official one (the methods were just wrappers anyway).
I've also moved the remaining methods into the utils package.
