function_graph: Use bitmask to loop on fgraph entry

function_graph: Use bitmask to loop on fgraph entry

Instead of looping through all the elements of fgraph_array[] to see if
there's an gops attached to one and then calling its gops->func(). Create
a fgraph_array_bitmask that sets bits when an index in the array is
reserved (via the simple lru algorithm). Then only the bits set in this
bitmask needs to be looked at where only elements in the array that have
ops registered need to be looked at.

Note, we do not care about races. If a bit is set before the gops is
assigned, it only wastes time looking at the element and ignoring it (as
it did before this bitmask is added).

Link: https://lore.kernel.org/linux-trace-kernel/20240603190824.604448781@goodmis.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Florent Revest <revest@chromium.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: bpf <bpf@vger.kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Guo Ren <guoren@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>