feat: Centralized Request Processing middleware

[dave-gray101]

This PR reworks how our endpoints parse and process user input, in order to centralize and commonize that code as much as possible. This will drastically cut down the endpoint-specific code to a minimum.

Additionally, the VAD subsystem was untested - making it hard to validate if this changeset was safe or not. Therefore, this PR also adds both manual testing tools (via bruno) and automated testing in the AIO image.

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Note to @mudler - this PR looks worse than it is - here's some reviewing notes to help

• core/http/middleware/request.go should be where you start - its the heart of the change and replaces core/http/ctx/fiber.go
• configuration of defaults is now a responsibility of the route function - seems a bit weird at first, but allows endpoints to be easily reused with different defaults on different paths.
• while all the endpoint files were updated, the changes all follow the same pattern:
  • A new standard header to the function was added which pulls the relevant input and config from the earlier middleware stage
  • A bunch of code is deleted as its now performed earlier by those middlewares
  • The functional code specific to the endpoint is unchanged except for variable references
• Specific to the AIO CI test: I was seeing very unpredictable behavior on CI versus locally reproducing this test. It turns out that setting LOCALAI_SINGLE_ACTIVE_BACKEND=true helps with a memory usage issue!