httpc-based implementation of hex_http contract.

Configuration keys:

* profile - the name of the profile, defaults to default. See httpc:set_options/2 for more information on setting options on profiles.

* http_options - a list of HTTP options, defaults to []. See httpc:request/5 for a list of available HTTP options. Without an {ssl, SslOpts} option, HTTPS requests verify the server certificate against the CA certificates from public_key:cacerts_get/0, and fail with {error, {cacerts_unavailable, Reason}} when those can't be loaded, which is always the case on OTP 24.