Incorrect formatting of import clause line comments

[HT154]

Pkl 0.30.2 formats this:

import "pkl:json" // used for doc comments
import "pkl:jsonnet"
import "pkl:math" // used for doc comments
import "pkl:pklbinary"
import "pkl:protobuf"
import "pkl:xml"
import "pkl:yaml" // used for doc comments

To:

// used for doc comments

// used for doc comments

// used for doc comments
import "pkl:json"
import "pkl:jsonnet"
import "pkl:math"

[stackoverflow]

The formatter doesn't associate comments to nodes, so when it reorders imports it doesn't touch the comments.
For trailing comments we could add some heuristic that tries to keep them glued to their imports. For non-trailing imports it's not possible to generate a heuristic that always works (which is probably why Google's java format and ktfmt don't do it either).
The empty lines between them are ugly and should be fixed, though.