Add bpf_get_current_comm support in ebpf_helper.

Please help add this helper function to allow eBPF program knows the executable name, it could improve our eBPF logic to avoid the redirection for some particular executables.

long bpf_get_current_comm(void *buf, u32 size_of_buf)

Description
Copy the comm attribute of the current task into
buf of size_of_buf. The comm attribute contains the
name of the executable (excluding the path) for the
current task. The size_of_buf must be strictly
positive. On success, the helper makes sure that
the buf is NUL-terminated. On failure, it is filled
with zeroes.

Return 0 on success, or a negative error in case of
failure.

Start by locating ebpf_helper and the existing eBPF helper implementations that define how helpers are exposed and tested. Use the stated bpf_get_current_comm signature and semantics as the acceptance criteria: copy the current executable name, NUL-terminate successful results, zero the buffer on failure, and return the documented status.

Written by the indexing model from the issue text.