Align http span data to convention

[stefanosiano]

Description

There are few http data keys that are different from our convention
I’m talking mainly about method and response_body_size that should be http.method and http.response_content_length in breadcrumb and http span

[marandaneto]

@stefanosiano would you like to take this PR? so you get a filling of the SDK, PRs, code reviews, how to run tests, etc? I can guide :) it should be pretty much a ctrl c - ctrl v + fixing test.

[stefanosiano]

yeah, sure!