implement Open Inference Protocol endpoints

[drbh]

This PR adds support for the Open Inference Protocol (V2 Inference Protocol) with the following routes

Endpoint	Category	Action	Method	Request Payload	Response Payload
v2/models/[/versions/<model_version>]/infer	Inference		POST	$inference_request	$inference_response
v2/models/<model_name>[/versions/<model_version>]	Model	Metadata	GET	-	$metadata_model_response
v2/health/ready	Server	Ready	GET	-	$ready_server_response
v2/health/live	Server	Live	GET	-	$live_server_response
v2	Server	Metadata	GET	-	$metadata_server_response
v2/models/<model_name>[/versions/]/ready	Model	Ready	GET	-	-

docs: https://kserve.github.io/website/0.12/modelserving/data_plane/v2_protocol/#open-inference-protocol-v2-inference-protocol

note: server must be built with --features kserve

[drbh]

this PR should be ready to merge, I was originally going to add unit tests before promoting from a draft PR however all meaningful changes are limited to new HTTP endpoints and new structs and currently we are not testing these things as unit tests. I will add tests for these additions in the repo that builds the container.

Please let me know if there are any tests I should add or changes I should make!