Get rid of backtrace machinery

It is currently very fragile, due to:

* Differing versions of compilers/DWARF version result in a variety
    of breakages in the our code which analyzes the DWARF info;

* With musl, libunwind seems to be currently unable to traverse
    beyond signal handlers, due to the DWARF information not
    being present in the signal frame.
    See <https://maskray.me/blog/2022-04-10-unwinding-through-signal-handler>.
    Note that I have not verified that the problem in the blog
    post above is indeed what we're hitting, but it seems plausible.

cpp/core/Exception.hpp

@@ -17,12 +17,7 @@ const char *translateErrno(int _errno);
 
 class AbstractException : public std::exception {
 public:
-    AbstractException();
-    const char * getStackTrace() const;
     virtual const char *what() const throw() override = 0;
-
-private:
-    char _stacktrace[4000];
 };