Merge all bpf programs into one

Multiple bpf program can be stored the same binary and we can extract
them one by one according to their function name elf header at run time.
Store them in one file can reduce the load time by only open one binary
file once. Rewrite the elf parser with Slice support.

Test: phone boot and eBPF program is loaded and pinned.
Bug: 78132446
Change-Id: I96dba91a69654fcac2c022100e954d8b0c4e0718