Realign on the issue triage process

**Describe the problem/challenge you have**
We have a [documented issue triage process](https://github.com/vmware-tanzu/carvel/blob/develop/processes/issue-triage.md) but it's been a while since we last discussed it. Because of this, there is some misalignment behind our triage process which causes confusion for maintainers.

**Describe the solution you'd like**
Alignment around our triage process:
- Maintainers (and prospective maintainers) know what's expected of them regarding the triage process.
- We have documented steps for performing issue triage.
- We have automated or streamlined as much of the triage process as possible.

**Anything else you would like to add:**
- Consider if there are issue template updates that can be made to streamline triaging (for example, requester provide their priority of an issue).
- Are there GitHub Project features we can utilize?
- Keep in mind that we have a separate ticketing for aligning on our labeling system (#211)

Start by reading processes/issue-triage.md and reviewing the current issue templates. Define the expected maintainer triage steps, identify GitHub Projects features that may help, and determine which parts can be streamlined or automated. Done means the triage process is aligned and its steps and supporting changes are documented.

Written by the indexing model from the issue text.