refactor: remove starter and premade from cody.json

[abeatrix]

RE: https://sourcegraph.slack.com/archives/C05AGQYD528/p1693983800785199

refactor: remove starter and premade fields from custom config

• Removed the starter and premade fields from the MyPrompts and MyPromptsJSON interfaces in the prompts module.
• Removed usage of the premade field in the MessageProvider class.
• Removed logs and telemetry related to the custom premade field.

Seems like permade was not working before as well so no harm in removing it

Follow up

Move starter config option to user/workspace config

Test plan

• set starter and premade in your cody.json
• Check the output log, the starter and premade strings should not be found anywhere in the output:
  
  

Before: