* [ML][Inference] adds lazy model loader and inference (#47410)

This adds a couple of things:

- A model loader service that is accessible via transport calls. This service will load in models and cache them. They will stay loaded until a processor no longer references them
- A Model class and its first sub-class LocalModel. Used to cache model information and run inference.
- Transport action and handler for requests to infer against a local model
Related Feature PRs: 
* [ML][Inference] Adjust inference configuration option API (#47812)

* [ML][Inference] adds logistic_regression output aggregator (#48075)

* [ML][Inference] Adding read/del trained models (#47882)

* [ML][Inference] Adding inference ingest processor (#47859)

* [ML][Inference] fixing classification inference for ensemble (#48463)

* [ML][Inference] Adding model memory estimations (#48323)

* [ML][Inference] adding more options to inference processor (#48545)

* [ML][Inference] handle string values better in feature extraction (#48584)

* [ML][Inference] Adding _stats endpoint for inference (#48492)

* [ML][Inference] add inference processors and trained models to usage (#47869)

* [ML][Inference] add new flag for optionally including model definition (#48718)

* [ML][Inference] adding license checks (#49056)

* [ML][Inference] Adding memory and compute estimates to inference (#48955)

* [ML][Inference] adds lazy model loader and inference (elastic#47410)

This adds a couple of things:

- A model loader service that is accessible via transport calls. This service will load in models and cache them. They will stay loaded until a processor no longer references them
- A Model class and its first sub-class LocalModel. Used to cache model information and run inference.
- Transport action and handler for requests to infer against a local model
Related Feature PRs:
* [ML][Inference] Adjust inference configuration option API (elastic#47812)

* [ML][Inference] adds logistic_regression output aggregator (elastic#48075)

* [ML][Inference] Adding read/del trained models (elastic#47882)

* [ML][Inference] Adding inference ingest processor (elastic#47859)

* [ML][Inference] fixing classification inference for ensemble (elastic#48463)

* [ML][Inference] Adding model memory estimations (elastic#48323)

* [ML][Inference] adding more options to inference processor (elastic#48545)

* [ML][Inference] handle string values better in feature extraction (elastic#48584)

* [ML][Inference] Adding _stats endpoint for inference (elastic#48492)

* [ML][Inference] add inference processors and trained models to usage (elastic#47869)

* [ML][Inference] add new flag for optionally including model definition (elastic#48718)

* [ML][Inference] adding license checks (elastic#49056)

* [ML][Inference] Adding memory and compute estimates to inference (elastic#48955)

* [ML] ML Model Inference Ingest Processor (#49052)

* [ML][Inference] adds lazy model loader and inference (#47410)

This adds a couple of things:

- A model loader service that is accessible via transport calls. This service will load in models and cache them. They will stay loaded until a processor no longer references them
- A Model class and its first sub-class LocalModel. Used to cache model information and run inference.
- Transport action and handler for requests to infer against a local model
Related Feature PRs:

* [ML][Inference] Adjust inference configuration option API (#47812)

* [ML][Inference] adds logistic_regression output aggregator (#48075)

* [ML][Inference] Adding read/del trained models (#47882)

* [ML][Inference] Adding inference ingest processor (#47859)

* [ML][Inference] fixing classification inference for ensemble (#48463)

* [ML][Inference] Adding model memory estimations (#48323)

* [ML][Inference] adding more options to inference processor (#48545)

* [ML][Inference] handle string values better in feature extraction (#48584)

* [ML][Inference] Adding _stats endpoint for inference (#48492)

* [ML][Inference] add inference processors and trained models to usage (#47869)

* [ML][Inference] add new flag for optionally including model definition (#48718)

* [ML][Inference] adding license checks (#49056)

* [ML][Inference] Adding memory and compute estimates to inference (#48955)

* fixing version of indexed docs for model inference