PR28557: module probe insertion on modern kernels

PR28557: module probe insertion on modern kernels

For reasons not completely understood, kernels in the 5.* range have
stopped taking module kprobes registrations of the form the runtime
has offered them.  New code in runtime/linux/kprobes.c
(stapkp_prepare_kprobe) now tried to fully relocate addresses itself,
rather than letting the kernel try it with symbols / kallsyms.

Added more diagnostic prints in nearby symbol/kprobe code paths and a
few more error checks in transport.