v3.5.3: handle ESRCH in more ptrace callsites (#91)

we are seeing processes exit with the following:

```
run process: run_parent03:44
Caused by:03:44
    0: handle_syscall pid=11203:44
    1: get_target_path03:44
    2: ptrace::getregs03:44
    3: ESRCH: No such process
```

a traced process can exit at any time so any ptrace calls that operate
on the pid must check esrch to see if the traced process has exited and
handle it appropriately

we already do it in a bunch of places but do it in more