Refactor elf parsing code to a seperate library

The elf parsing and program loading code of bpfLoader can be reused in
future. Adding them to libbpf as a helper function.

Bug: 79171384
Test: device boot and dumpsys netd show eBPF object okay.
Change-Id: If3d1a37e84065e9d9e7c7438f161b594c05c7663
4 files changed