fix(execve): reset signal handlers and clear pending signals on execve

fix(execve): reset signal handlers and clear pending signals on execve

POSIX requires that execve resets all signal handlers to SIG_DFL
(except SIG_IGN) and clears pending signals. Without this, the
kernel could attempt to deliver a signal to a handler address in
the destroyed old address space, causing a crash.

Also removed debug trace code (ldso trace, write trace, exit trace,
PTE dumps, GOT dumps) that was added during debugging and was
interfering with test output.