[FEATURE] pyroscope: migrate profile queries to the Connect API

[luweglarz]

Description

/render is documented as Pyroscope's legacy HTTP API: https://grafana.com/docs/pyroscope/latest/reference-server-api/#querying-profile-data

This PR is to migrates the Pyroscope plugin's profile queries from the legacy GET /pyroscope/render
endpoint to Pyroscope's Connect API that is decoupled in 2 endpoints:

• SelectMergeStacktraces for the flame graph
• SelectSeries for the timeline

this brings profile querying in line with the rest of the pyroscope-client, which already used Connect for profile types, label names, and label values.

• The request is now split into two parallel calls instead of one.
• ProfileData's shape returned to the panel is unchanged, so FlameChartPanel and itssubcomponents needed no changes.
• Added test coverage for getProfileData itself (previously untested), covering request
  building, the time-range fallback, and response assembly.

Checklist

• Pull request has a descriptive title and context useful to a reviewer.
• Pull request title follows the [<catalog_entry>] <commit message> naming convention using one of the
  following catalog_entry values: FEATURE, ENHANCEMENT, BUGFIX, BREAKINGCHANGE, DOC,IGNORE.
• All commits have DCO signoffs.