Support label multiselection

[wd60622]

Describe what this PR does / why we need it

Allows user to allow multiselect for adding and removing labels

Related to #675

Does this pull request fix one issue?

Describe how you did it

• Adapt the graphql command to pass list of labelIds
• Generalize telescope logic to grab multiple selection and check if non-empty
• Use callback on list of labels including list of single label

Describe how to verify it

For telescope, use <Tab> to select multiple labels (while adding or removing) then press enter to confirm. If Tab is not pressed, then the behavior will be the same as before.

Special notes for reviews

Telescope only. However, fzf had support before but the cb was changed to support batch label add.

Checklist

• Passing tests and linting standards
• Documentation updates in README.md and doc/octo.txt

[wd60622]

Luckily reviewers and assignees is very similar. Will address in the near future as well