Wrap process changes in a locked transaction

[#79386676]
Fix unexpected modification on updating processes through repository

[#79386676]
Operator switching CC Diego flags correctly switches behaviour of apps opted-in to Diego [#80165482]

Also, refactor bulk endpoints to use backends
Rename find_one_to_x => x-ing_backend_for_app [#80165482]
Simplify Backends interface, validate StagingCompletion only handles Diego apps. [#80165482]
Refactor Backends into three

* Stagers - know about staging
* Runners - know about running
* InstancesReporters - know how to report

[#80165482]
HM9000 needs to check for Diego on stop app

* When Diego is enabled, the HM9000 needs to stop any app that is marked
* for running on Diego.

[#80165482]
Fix the damn rebase
Merge branch 'diego-dea-alternating-80165482' of https://github.com/cloudfoundry/cloud_controller_ng into diego-dea-alternating-80165482