Move from stale bot to stale action

[mathomp4]

Types of change(s)

• 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)
• Trivial change (affects only documentation or cleanup)
• Refactor (no functional changes, no api changes)

Checklist

• Tested this change with a run of GEOSgcm
• Ran the Unit Tests (make tests)

Description

Today I thought to myself "Hey, I haven't seen a stalebot ping in a while" and, yep, it was shutdown like a year ago and I never noticed. So, per their advice, we move to use the Stale GitHub Action.

The configuration is:

• Issues: Stale at 60 days, close 7 days later
• PRs: Stale at 60 days, close 30 days later

I think the Stale and Long Term labels should prevent it from acting, but we will see.

Related Issue