Adding cancellation to background handlers to prevent agent from being held open

[aryanjassal]

Description

Often, some background task handlers hold the agent open when we are trying to shutdown. The only solution is to send a SIGKILL to the process to forcefully shut it down. This should not happen.

Issues Fixed

• Fixes polykey agent stop command not terminating properly Polykey-CLI#185 (FIX ENG-322)

Tasks

• 1. Add cancellation to Discovery.discoverVertexHandler
• 2. Add cancellation to NodeManager.syncNodeGraphHandler
• 3. Add cancellation to NodeManager.checkConnectionsHandler
• 4. Add cancellation to NodeManager.refreshBucketHandler

Final checklist

• Domain specific tests
• Full tests
• Updated inline-comment documentation
• Lint fixed
• Squash and rebased
• Sanity check the final build

[linear]

ENG-322

[aryanjassal]

There were some weird issues happening when I attempt to link Polykey's dist directory to Polykey CLI's node_modules for testing the changes. This was resolved by simply copying the dist for Polykey instead of linking it. I believe this was due to the libraries not aligning when using linking.

[tegefaulkes]

You've added @timedCancellable(true) all over the place. Keep in mind that without a default timeout provided then it will default to infinite timeout. In most cases we don't want this. Check what the existing @timedCancellable usage for each file is doing.