bpftool: Add support for dumping streams

bpftool: Add support for dumping streams

Add support for printing the BPF stream contents of a program in
bpftool. The new bpftool prog tracelog command is extended to take
stdout and stderr arguments, and then the prog specification.

The bpf_prog_stream_read() API added in previous patch is simply reused
to grab data and then it is dumped to the respective file. The stdout
data is sent to stdout, and stderr is printed to stderr.

Cc: Quentin Monnet <qmo@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20250703204818.925464-12-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>