runtime: add kernel user perf event array and per cpu array

[Officeyutong]

WIP

Todos:

• Add support for kernel user per cpu array map
• Add support for kernel user perf event map

Details

Shared perf event array map is implemented in such way:

• It was backed with a real kernel perf event array, and a user ring buffer
• When a userspace ebpf program wants to output to the perf array, it writes its data into the user ringbuffer.
• A kernel ebpf program will be attached to an intervally-triggered perf event. It keeps draining data from the user ringbuffer, then (if available) output the data into the kernel perf event.

Use examples/libbpf-tools/bashreadline to test the shared user perf event array.