Merge branch 'support-freplace-prog-from-user-namespace'

Mykyta Yatsenko says:

====================
Support freplace prog from user namespace

From: Mykyta Yatsenko <yatsenko@meta.com>

Freplace programs can't be loaded from user namespace, as
bpf_program__set_attach_target() requires searching for target prog BTF,
which is locked under CAP_SYS_ADMIN.
This patch set enables this use case by:
1. Relaxing capable check in bpf's BPF_BTF_GET_FD_BY_ID, check for CAP_BPF
instead of CAP_SYS_ADMIN, support BPF token in attr argument.
2. Pass BPF token around libbpf from bpf_program__set_attach_target() to
bpf syscall where capable check is.
3. Validate positive/negative scenarios in selftests

This patch set is enabled by the recent libbpf change[1], that
introduced bpf_object__prepare() API. Calling bpf_object__prepare() for
freplace program before bpf_program__set_attach_target() initializes BPF
token, which is then passed to bpf syscall by libbpf.

[1] https://lore.kernel.org/all/20250303135752.158343-1-mykyta.yatsenko5@gmail.com/
====================

Link: https://patch.msgid.link/20250317174039.161275-1-mykyta.yatsenko5@gmail.com
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>