Add sendHttpRequest mutation to send schemaless HTTP requests

[hgiasac]

Add a new sendHttpRequest mutation to send schemaless HTTP requests. It's used as a dynamic GraphQL to REST proxy.

mutation {
  sendHttpRequest(
    body: {
      id: 101,
      title: "Hello world",
      userId: 10,
      body: "A test post"
    }
    method: "post"
    url: "https://jsonplaceholder.typicode.com/posts"
  )
}

[github-actions]

Package	Line Rate	Health
github.com/hasura/ndc-http/connector	62%	➖
github.com/hasura/ndc-http/connector/internal/argument	52%	➖
github.com/hasura/ndc-http/connector/internal	55%	➖
github.com/hasura/ndc-http/connector/internal/contenttype	56%	➖
github.com/hasura/ndc-http/connector/internal/security	60%	➖
github.com/hasura/ndc-http/ndc-http-schema/configuration	40%	➖
github.com/hasura/ndc-http/ndc-http-schema/openapi/internal	49%	➖
github.com/hasura/ndc-http/ndc-http-schema/openapi	40%	➖
github.com/hasura/ndc-http/ndc-http-schema/schema	32%	❌
github.com/hasura/ndc-http/ndc-http-schema/utils	43%	➖
github.com/hasura/ndc-http/ndc-http-schema/version	26%	❌
Summary	49% (4362 / 8968)	➖

Minimum allowed line rate is 40%