Add install/uninstall/activate/deactivate hooks to pub

[sethladd]

To repro:

pub global activate stagehand
mkdir empty
cd empty
stagehand webapp
  (say Y to analytics)
pub global deactivate stagehand

cat ~/.stagehand

Expected: ~/.stagehand file is deleted (or, a notice is sent to stagehand that the package is getting deleted)

Actual: apparently (?) no signal on uninstall

[sethladd]

If there's a lifecycle callback that pub is sending, and that stagehand is not listening to, please let us know and then close this issue. :) Thanks for taking a look!

[nex3]

Pub doesn't currently support any package hooks of any kind, but we may in the future. I'm retargeting this issue to that.

---

Removed Priority-Unassigned, Pub-Global labels.
Added Priority-Low label.
Changed the title to: "Add install/uninstall/activate/deactivate hooks to pub".

[sethladd]

sgtm

[DartBot]

This issue has been moved to dart-lang/pub#1192.