debuginfod: Only download debug info for hot functions

[Desour]

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Is your feature request related to a problem? Please describe. The debuginfod integration is great to have! But using hotspot on an application for the first time (or after an upgrade) can take very long, because it has to download sometimes multiple GiBs of debug info. This also uses up some of my disk space. And most of the libs are not relevant for the performance bottleneck that you want to investigate.

Describe the solution you'd like Don't download debug info on startup when loading perf data. Instead make it so that the user can rightclick on a function and choose to download the debug info for only that function's binary.

Describe alternatives you've considered Download the debug info in background, so the user can look at the output earlier, but without function signatures.

Additional context None