This commit modifies the `DebuggerStats::ReportStatistics`
implementation to avoid loading symbol files for unloaded symbols. We
collect stats on debugger shutdown and without this change it can cause
the debugger to hang for a long while on shutdown if they symbols were
not previously loaded (e.g. `settings set target.preload-symbols
false`).
The implementation is done by adding an optional parameter to
`Module::GetSymtab` to control if the corresponding symbol file will be
loaded in the same way that can control it for `Module::GetSymbolFile`.
1d1b20a19e