refactor: shared memory client

[Officeyutong]

Refactor the shared memory client and libraries. Including these targets:

• bpftime_shm_client: Provide client for operating things stored in shm. Such as bpf_map_lookup_elem, bpf_prog_load, etc. And provide implementation of shared/userspace maps, and handlers

After this, we could limit the dependency to boost and libbpf to these targets. Other parts of bpftime runtime will be more dependent.

• [ ] Implement new shared memory client
• [ ] Implement new shared memory library
• [ ] Docs

[Officeyutong]

Not planned now