refactor: deprecate cortex configs

[louis-jan]

Describe Your Changes

• There is no need to introduce a generic configurations endpoint for use globally in Cortex. So every engine update could go under /engines/[engine] and cortex engines [engine] set
• Return engine configuration values is also an anti-pattern. Client should not know configured values In order to support multiple users, authentication but just the status of the engine: (e.g. not configured, not initialized)
• Deprecated cortex kill command

To update an engine via REST API:
PATCH: /engines/[engine]

{
     "config": "openai",
     "value": "sk-xxxxxx"
}

To update an engine via CLI:

cortex engines <engine> set <config> <value>

Get engine response via /engines/[engine] or cortex engines [engine] get

{
      "name": "<name>",
      "description": "<description>",
      "version": "<version>",
      "productName": "<productName>",
      "status": "<status>",
}

Available engine statuses:

'ready', // Engine is ready to use
'missing_configuration', // Engine is missing configurations
'not_initialized', // Engine is not intialized
'error', // General error

Fixes Issues

• Closes #

Self Checklist

• Added relevant comments, esp in complex areas
• Updated docs (for bug fixes / features)
• Created issues for follow-up changes or refactoring needed

[louis-jan]

Updated: there is no /update under /engines/[engine]. Just Patch