Fix missing remote read spans (#7914) (#7916)
Fix missing remote read spans (#7914) (#7916)

The remote read client needs to use the nethttp.Transport wrapper in
order for spans to be instrumented properly.

Signed-off-by: Chris Marchbanks <0ad0b538c51a24737b83a297dff91636ee98d89e@gmail.com>

Co-authored-by: Chris Marchbanks <0ad0b538c51a24737b83a297dff91636ee98d89e@gmail.com>
GoogleCloudPlatform/prometheus,alileza/prometheus,alileza/prometheus,keegancsmith/prometheus,alileza/prometheus,keegancsmith/prometheus,keegancsmith/prometheus,prometheus/prometheus,GoogleCloudPlatform/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,prometheus/prometheus,keegancsmith/prometheus,alileza/prometheus,GoogleCloudPlatform/prometheus,GoogleCloudPlatform/prometheus,prometheus/prometheus,keegancsmith/prometheus,prometheus/prometheus,prometheus/prometheus