Add Stale action to TSC project issues and pull requests

[bcantoni]

This project has a very long backlog of old issues, most of which have probably aged out and won't be a priority for solving. Today we have almost 200 issues, the oldest of which is from 2017.

We're better keeping up with PRs: only 17 open, 3 of which are from 2024.

To help manage this better, I propose adding https://github.com/actions/stale which "Warns and then closes issues and PRs that have had no activity for a specified amount of time."

There are a lot of fine-grained controls, but for discussion what if we start with the default configuration behavior:

• Add a label "Stale" on issues and pull requests after 60 days of inactivity and comment on them
• Close the stale issues and pull requests after 7 days of inactivity
• If an update/comment occur on stale issues or pull requests, the stale label will be removed and the timer will restart

We can also define a specific lable like save that would keep that Issue/PR open indefinitely.

@jacalata and @jorwoods what do you think?