http-client instrumentation using hooks

[kakkun61]

What

• to use managerModifyRequest and managerModifyResponse to implement this instrumentation
  • instead of wrapping original http-client's Manager

Why

• a lot of wrapping and unwrapping are necessary because the wrapper type is different from the original one of course when using http-client instrumentation

How

• ManagerSetting provides hooks for requests and responses
• to call createSpan in a hook for a request and to call endSpan in a hook for a response
• ThreadLocalStorage is used to transport span data created in a hook for a request to a hook for a response

Note

Cachix @sandydoo seems to implement a similar instrumentation.

https://github.com/cachix/hs-opentelemetry-instrumentation-http-client/

This PR includes diffs of #142.