Revamp the triaging process

[mx-psi]

We have a triaging role but its scope, duties and actual day-to-day responsibilities are not entirely clear. To improve this, here is a list of items that I believe we should work on:

• Review existing labels and define set of labels for triaging and their meaning #36676
• Define states an issue can be at #36677
• Describe triaging process in detail #36678
• Define how triaging process is done #36679

There are also other items that I think should be considered by the triaging team, including ensuring the SIG can:

• Track unmaintained components and unresponsive codeowners
• Triage PRs that we have not responded to
• Ensuring the SIG meeting is organized in a way that allows issues to be responded to
• Track trends week over week

I think we can file a separate issue for these, but still I believe they are worth mentioning here to guide the decision making on the other ones.

See also open-telemetry/opentelemetry-collector/issues/11802