airframe-http: Use HttpMessage.Request/Response as the standard interface

[xerial]

Historically, we needed to manage various http request/response types of Finagle, OkHttp, etc. Now that airframe-http has its own HttpMessage.Request/Response types, we should be able to wrap backend-specific request/response types into the unified http requests and responses.

Converting backend specific requests (e.g., Fingagle request) to HttpMesage.Request is not expensive. Currently, using backend-specific implementation has much higher cost.

Projects using backend-specific request/response types:

• airframe-http-okhttp
• airframe-http-finagle
• airframe-http-recorder
• airframe-http-grpc

Benefits:

• We can use the same filters both for finagle and gRPC (e.g., auth filter, header manipulation filter, etc.)
• Simplify the usage of http-recorder, okhttp, etc.

Steps:

• Add a new factory methods in each projects
• Preserve the current interfaces for a while so as not to break the existing code

[xerial]

done