This PR is an ALTERNATIVE to #2392 . See https://github.com/dave-gray101/LocalAI/pull/1/files for a diff.

• If we don't want to merge "dead code walking" in the form of core/http/ctx we can skip over 2392 and go straight to 2440. Normally, I'd say this is a pretty minor concern, but given that these PRs have been difficult to find safe merge windows for, I'm concerned that it could cause more work for us to leave it be.
• If we care more about "touching less" at once, as I expect, this PR will likely be rebased into the next PR, which is expected to touch the core/http/endpoints/openai folder anyway.

This PR should not be set to auto merge right now - I want to manually check that diff before merging the final versions.

This PR is the start of transitioning our core services to the core/application.go \ core/startup model.
In order to keep things reviewable, this PR will have a limited scope - rather than moving everything at once, my goal is to select services that are covered by existing tests for the detection of regressions. Therefore, this PR contains the following components:

• begins the creation of http/middleware, migrating request object handling outside the endpoints themselves.
• • also takes over some existing middleware to this new folder, for organizational reasons.
• Finishes up service wiring infrastructure in core/startup
• pkg/concurrency - basic JobResult structure
• Port over TTS Endpoints to TextToSpeechBackendService
• Port over Embedding Endpoint to EmbeddingBackendService