Make use of standard opentracing tags

[dadrus]

The Opentracing sematic conventions document "standardizes" some tags for different purposes, many APM implementations rely on these to properly display traces & spans.

Unfortunately this project does not make use of these. My proposal is to change this:)

This would mean e.g. in addtion or instead of having

span := c.GetSpan(ctx).NewChild(OpSQLTxBegin)
span.SetLabel("component", "database/sql")

one would have

span := c.GetSpan(ctx).NewChild(OpSQLTxBegin)
span.SetLabel("component", "luna-duclos")
span.SetLabel("db.type", "sql")

in all relevant places. Actually the component tag should be set by a calling app, so it should be configurable. In addition all places with

span.SetLabel("query", query)
if !c.OmitArgs {
    span.SetLabel("args", formatArgs(args))
}

would be changed to

span.SetLabel("db.statement", query)
if !c.OmitArgs {
    span.SetLabel("args", formatArgs(args))
}

Last, but not least, db.instance tag should be set as well.

If backwards compatibility is required, it could be achieved by the introduction of additional options. If you like I can create a PR.

[mellester]

Nice job @dadrus ill make use of your fork and keep track of erros