prometheus: use the metrics layer instead of the scollectd
prometheus: use the metrics layer instead of the scollectd

The metrics layer is a base for different metrics and metrics reprting
API.

This changes the prometheus API to use the new metrics layer.

Signed-off-by: Amnon Heiman <ed5fc74c4692051ad0b19749fd7cea6ec2d74b9e@scylladb.com>

cloudius-systems/seastar,avikivity/seastar,avikivity/seastar,syuu1228/seastar,scylladb/seastar,dreamsxin/seastar,cloudius-systems/seastar,syuu1228/seastar,scylladb/seastar,dreamsxin/seastar,dreamsxin/seastar,scylladb/seastar,avikivity/seastar,syuu1228/seastar,cloudius-systems/seastar