feat(incident): add incident reopen command

Description

Add incident reopen command to reopen resolved incidents.

Note: There are two commits in the MR. First commit moves issue reopen code into issuable directory. We need to avoid squashing commits on merge to keep the commit history for that file.

Related Issues

Resolves #1314 (closed)

How has this been tested?

With tests and manually executing commands from the command line.

• glab issue reopen <INCIDENT_ID>
• glab incident reopen <INCIDENT_ID>
• glab incident reopen <ISSUE_ID>
• glab incident reopen --help

Screenshots (if appropriate):

issue reopen	incident reopen	incident reopen error	incident reopen --help

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation
• Chore (Related to CI or Packaging to platforms)
• Test gap