feat: add bulkdeploy related variables to builds

[shreddedbacon]

Checklist

• Affected Issues have been mentioned in the Closing issues section
• Documentation has been written/updated
• PR title is ready for changelog and subsystem label(s) applied

Add 3 new build scope variables relating to bulk deployments

LAGOON_BULK_DEPLOY = true
LAGOON_BULK_DEPLOY_ID = the UUID of the bulk deploy
LAGOON_BULK_DEPLOY_NAME = the name of the bulk deploy if provided

Also adding the priority too, for all builds that have a priority

LAGOON_BUILD_PRIORITY = the priority number of the build