`gh issue links` outputs active issues and the number of references in other issues or comments

### Describe the feature or problem you’d like to solve

An addition to `gh issue` that adds a command `links`.
- With no further option, this command will list out all active issues and the amount of times they are linked by another issue (active or non-active) directly (an immediate link to the issue an issue or comment) or indirectly (a link to an issue that directly links to the issue in question)
- With an issue number as an option this will print out 2 lists of issues. 1 list of directly linked issues and 1 list of indirectly linked issues.

### Proposed solution

The benefit of this is code triage as well as a way for users looking through issues to follow an indirect trail of linked issues in order to get help to fix their problem, and for developers to get a better sense of the information they have at hand for a problem.

Solution: parse an open issue, if it has any links to other issues or PRs, count them as directly linked. For all directly linked issues or PRs, scan through them and if there are any other issues linked, count those as indirectly linked.

### Additional context

```
gh issue links
ISSUE DIR INDIR
2190 1 3
2220 2 1
3210 1 0
3560 0 0
4001 0 0
4390 2 0
4440 6 4

gh issue links 2190
Directly linked
2220
Indirectly linked
3210
4001
3560
```

In this above example:
- 2220 has a direct link to 2190
- 3210 and 4001 directly link to 2220
- 3560 directly links to 3210, which gives an indirect link to 2220