bpf: Add show_fdinfo for perf_event

After commit 1b715e1b ("bpf: Support ->fill_link_info for perf_event") add
perf_event info, we can also show the info with the method of cat /proc/[fd]/fdinfo.

kprobe fdinfo:
link_type:	perf
link_id:	10
prog_tag:	bcf7977d3b93787c
prog_id:	20
name:	bpf_fentry_test1
offset:	0x0
missed:	0
addr:	0xffffffffa28a2904
event_type:	kprobe
cookie:	3735928559

uprobe fdinfo:
link_type:	perf
link_id:	13
prog_tag:	bcf7977d3b93787c
prog_id:	21
name:	/proc/self/exe
offset:	0x63dce4
ref_ctr_offset:	0x33eee2a
event_type:	uprobe
cookie:	3735928559

tracepoint fdinfo:
link_type:	perf
link_id:	11
prog_tag:	bcf7977d3b93787c
prog_id:	22
tp_name:	sched_switch
event_type:	tracepoint
cookie:	3735928559

perf_event fdinfo:
link_type:	perf
link_id:	12
prog_tag:	bcf7977d3b93787c
prog_id:	23
type:	1
config:	2
event_type:	event
cookie:	3735928559

Signed-off-by: Tao Chen <chen.dylane@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250606150258.3385166-1-chen.dylane@linux.dev