Add draining for cc uploader

[kathap]

Enhance droplet upload to be more resilient:
Add shutdown logic for cc_uploader process in Drain class

- Implement `shutdown_cc_uploader` method to handle graceful and forceful shutdown of the cc_uploader process.
- Send `TERM` signal to initiate shutdown and wait for the process to terminate.
- If the process does not terminate within the specified timeout (=900seconds), send `KILL` signal to forcefully shut it down.
- Log appropriate messages during the shutdown process.

• A short explanation of the proposed change:
  The proposed change adds a new method shutdown_cc_uploader to the Drain class. This method handles the graceful and forceful shutdown of the cc_uploader process. It sends a TERM signal to initiate the shutdown and waits for the process to terminate. If the process does not terminate within the specified timeout (900 seconds), it sends a KILL signal to forcefully shut it down. The method also logs appropriate messages during the shutdown process.

• An explanation of the use cases your change solves
  If api VM gets stopped and starts draining, give upload jobs the chance to finish upload, initiate a graceful shutdown, allowing the process to terminate cleanly.

• Links to any other associated PRs
  Add draining for cc_uploader capi-release#529
  More resilient droplet upload cc-uploader#195

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• I have made this pull request to the main branch

• I have run all the unit tests using bundle exec rake

• I have run CF Acceptance Tests