Fixes for label discrepancies in collector for summaries etc which have
a template which includes a quantile.
Initial native Prometheus client implementation of metrics - which is
currently turned off except for local testing and interface exports.
This is a fix for
```cache_total{target="acc_read"} counter it's invalid syntax of metric type. prometheus parsing error```
which does not remove the whole metadata tag
This is a non functional change which consolidates the various packages
under metrics into the top level package now that the dead code is
removed.
It is a precursor to the removal of Victoria metrics after which all
erigon metrics code will be contained in this single package.
