[FEATURE] Add user friendly API for register events.

[yunwei37]

Is your feature request related to a problem? Please describe.

There should be a clearly API to allow user register events and init runtime.

Describe the solution you'd like

for example:

// Init runtime
int bpftime_init_runtime(runtime_config* config);
// Register events
int bpftime_register_attach_events(int event_id, event_config* config);
// Handle events
int handle_events(int event_id, struct ecent_ctx* ctx);

We need to discuss how to do that.

Describe alternatives you've considered

Provide usage examples

Additional context

[Officeyutong]

What does event here mean? Attach type?

[yunwei37]

for example, nginx incoming request is an event, uprobe is an event, syscall tracepoints is an event, dpdk incoming request can be an event

Events can be connected to bpf_prog using bpf_link.

[yunwei37]

Does that make sense?

[Officeyutong]

for example, nginx incoming request is an event, uprobe is an event, syscall tracepoints is an event, dpdk incoming request can be an event

Events can be connected to bpf_prog using bpf_link.

These were called attach type previously, but we need a full set of callbacks to define an attach type, such ad instantiation at https://github.com/eunomia-bpf/bpftime/blob/a6a132bfe6717a2f41a67ec646b44856d57c5714/runtime/src/attach/bpf_attach_ctx.cpp#L111

We can have a discussion when you have some time