RFC: Mark PR's as stale after 300 days, close them after another 60 if no activity

[FrankRay78]

Unlike bigger OSS projects with many multiple contributors, spectre.console seems to rely on most contributions from their respective subsystem maintainers (no disrespect or ill will towards the contributions from individuals who are non-maintainers - these are very much welcomed too).

Whilst the current codebase is well tested, stable, and used by many downstream projects, it does mean that the balance of issues opened vs bandwidth to fix is slightly squewed towards longer latency. Some issues will never find favour amongst individual maintainer/contributors, for reasons entirely personal to them. A lack of a bigger contributor community means these issues may never be addressed.

There is a very interesting thread on this topic, titled Decision needed: should we close stale PRs? and how many lapsed days are PRs considered stale?, which discusses this very issue, and where I took the proposal for 300 days to stale, then 60 days to close. One comment on the thread, material to my reasons for drafting this request for comment/proposal, was:

528 reply, (~186 self identified maintainers, ~342 self identified users).
In general both groups have about 2.5 to 3 time more respondent feeling that coming across a repo with more than 200 PR is worse than having a PR closed for inactivity (nb. my highlighting).

I would welcome any and all comments on the proposal, and/or the topic more generally, as myself and the other maintainers discuss this matter amongst ourselves.

cc: @spectreconsole/maintainers