V3 Apps have a name

- can be issued during create
- can be updated
- can be obtained through GET

[#79387438]
Refactor app controller logic

  - Created app handler to contain app domain logic
  - Removed app repository in favor of using sequel model directly
  - Factored domain logic from controller into app handler
  - Removed anemic appv3 domain model

[#79387438]
Add validations for the name field.

[#79387438]
Name field is optional on update.

- If the name field is not provided, perform a no-op, keeping
compatibility with v2/apps/:guid

[#79387438]
Update web process name when updating a v3 app's name.

[#79387438]
Update the name of a V3 app when updating from V2.

[#79387438]
Make v3_app_name migration the newest migration.
Only update the V3 app name if the V2 app has a web type.

[#79387438]