Support printing DSO context when symbols aren't avaliable

[ChrisDenton]

Currently backtraces don't print enough context when symbols aren't resolved in-process (for whatever reason). If someone wants to attempt symbolising out of process then it may be impossible from the backtrace alone.

Quoting @bjorn3:

To be able to actually symbolize the backtraces this would need to print both the path of the DSO (executable or dylib) and the offset within this DSO. It could be a dylib loaded at runtime and thanks to ASLR the exact location of DSOs can't be determined anymore after the fact unless we print it here.

This could take inspiration on what backtrace-rs does on Fuchsia which unconditionally does backtrace symbolication out of process.

[ChrisDenton]

Getting the offset could be done using module_base_address. But we don't expose a cross-platform way to get the module's path.