API and documentation actualization

[kolesnikovae]

Since Pyroscope tracing integration has been rearchitected, some of the configuration options and behaviour specifics should be revisited.

In fact, it makes sense to deprecate all the configuration options (for now) and remove all the tags but pyroscope.profile.id:

• We always set the span_name label
• Only the root span can have a profile
• URLs should not be written as span attributes (as this may cause a fairly serious overhead)

Also, profile_id label is not available in the query expressions and such query will always result in empty response