DX-5119: Execute drush deploy:hook at the end of blt drupal:update

[pfrenssen]

When running blt drupal:update we are currently missing a way to execute post update hooks after config import. Support for hook_deploy_NAME() has been added 2 years ago to Drush (ref. drush deploy command).

There was a feature request to completely replace blt drupal:update with drush deploy in #4252 but this idea was abandoned since we would lose the more advanced use cases that are supported in blt drupal:update (such as allowing separate core-only and config-split config management strategies).

Describe the solution you'd like
We are already doing the majority of the steps done by drush deploy, except running the deploy hooks. Would it be perhaps a good idea to run drush deploy:hook at the end of our current blt drupal:update process? This way we can keep our advanced use cases, and still offer a "standard" way for site owners to run update hooks after importing config.

[jcnventura]

I support this.

[jcnventura]

This should be closed now that #4612 was merged.