Win32 symbolizer does not call SymCleanup()

absl/debugging/symbolize_win32.inc implements the symbolizer code for win32. However, while it calls SymInitialize() to init the symbolizer, it never calls SymCleanup() to tear it down correctly.

Per https://docs.microsoft.com/en-us/windows/win32/api/dbghelp/nf-dbghelp-symcleanup, "Failure to call this function causes memory and resource leaks in the calling application".

Probably the safest solution would be to replace InitializeSymbolizer() with e. g. a Symbolizer scoping object that could handle initialization and cleanup.