[EPIC] gRPC JSON transcoding

[JamesNK]

Community issue - #167

This issue is for tracking tasks. Separate from the community issue to avoid notification spam.

• Rewrite serialization to use System.Text.Json
  • Write converters for protobuf types
  • Optimization
  • Use new System.Text.Json .NET 7 features
• Support server streaming
• Support HttpBody messages - https://grpc-ecosystem.github.io/grpc-gateway/docs/mapping/httpbody_messages/
• Configuration
  • Unbound handlers - https://grpc-ecosystem.github.io/grpc-gateway/docs/mapping/grpc_api_configuration/
  • JSON customization (e.g. formatting, long as string, type register, disallow unknown properties)
  • Error handler
• Swagger support
  • Option to output query parameters as swagger parameters
  • Read XML docs as swagger docs
• Move source to aspnetcore repo
• Improve documentation
• Performance testing
• Update Grpc.Core.Api to 2.45.0
  • Remove nullable todos
  • Support WriteAsync cancellation token