reporter: extend lifetime for cached elements

[florianl]

Similar to the reported issue #248 around lifetime of executables, the same issue happens for frames. So keep cached frame information alive.

[Gandem]

👋 As discussed in #248, using GetAndRefreshKeys() for the frames outer cache solves the issue for UNREPORTED / UNRESOLVED frames, however, for long / forever running large executables, there is the potential of increasing the inner map (map[libpf.AddressOrLineno]sourceInfo) without limit.

I'm personally onboard with merging this first then working on the inner map size issue, just wanted to highlight the tradeoff that was raised in #248 (comment) !

[florianl]

Thanks for pointing this out. As mentioned, there is a risk of increasing the inner map (map[libpf.AddressOrLineno]sourceInfo) without limit. I do also agree, that limiting this inner map should be a dedicated issue/task.