Add API to write process statistics into user-provided struct

[chrischtel]

Feature request

Currently, Sandbox stores process statistics internally and exposes them via getLastStats().
This is convenient, but less flexible if a caller wants to collect stats into their own data structure (e.g. when running many sandboxes in parallel).

Proposal

Add an overload such as:

bool run_with_stats(const std::string& path,
                    const std::vector<std::string>& args,
                    ProcessStats& outStats,
                    DWORD timeoutMs = INFINITE);