libbpf: Optimize kprobe.session attachment for exact function names

Detect exact function names (no wildcards) in
bpf_program__attach_kprobe_multi_opts() and bypass kallsyms parsing,
passing the symbol directly to the kernel via syms[] array.  This
benefits all callers, not just kprobe.session.

When the pattern contains no '*' or '?' characters, set syms to point
directly at the pattern string and cnt to 1, skipping the expensive
/proc/kallsyms or available_filter_functions parsing (~150ms per
function).

Error code normalization: the fast path returns ESRCH from kernel's
ftrace_lookup_symbols(), while the slow path returns ENOENT from
userspace kallsyms parsing.  Convert ESRCH to ENOENT in the
bpf_link_create error path to maintain API consistency - both paths
now return identical error codes for "symbol not found".

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@crowdstrike.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260302200837.317907-2-andrey.grodzovsky@crowdstrike.com