Should HTTP client metrics have url.scheme?

[lmolkova]

HTTP Client metrics do not have a scheme:

• scheme may be useful to break traffic down by http/https
• more importantly, we populate port based on scheme

  - ref: server.port
    requirement_level:
      conditionally_required: If not default (`80` for `http` scheme, `443` for `https`).

Populating port alone won't be sufficient since we still won't know the scheme used.