samples/bpf: convert to vmlinux.h with tracing programs

This commit replaces separate headers with a single vmlinux.h to
tracing programs. Thanks to that, we no longer need to define the
argument structure for tracing programs directly. For example, argument
for the sched_switch tracpepoint (sched_switch_args) can be replaced
with the vmlinux.h provided trace_event_raw_sched_switch.

Additional defines have been added to the BPF program either directly
or through the inclusion of net_shared.h. Defined values are
PERF_MAX_STACK_DEPTH, IFNAMSIZ constants and __stringify() macro. This
change enables the BPF program to access internal structures with BTF
generated "vmlinux.h" header.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Link: https://lore.kernel.org/r/20230818090119.477441-3-danieltimlee@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

samples/bpf: replace BPF programs header with net_shared.h

This commit applies "net_shared.h" to BPF programs to remove existing
network related header dependencies. Also, this commit removes
unnecessary headers before applying "vmlinux.h" to the BPF programs.

Mostly, endianness conversion function has been applied to the source.
In addition, several macros have been defined to fulfill the INET,
TC-related constants.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Link: https://lore.kernel.org/r/20230115071613.125791-9-danieltimlee@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

samples/bpf: split common macros to net_shared.h

Currently, many programs under sample/bpf often include individual
macros by directly including the header under "linux/" rather than
using the "vmlinux.h" header.

However, there are some problems with migrating to "vmlinux.h" because
there is no definition for utility functions such as endianness
conversion (ntohs/htons). Fortunately, the xdp_sample program already
has a function that can be replaced to solve this problem.

Therefore, this commit attempts to separate these functions into a file
called net_shared.h to make them universally available. Additionally,
this file includes network-related macros that are not defined in
"vmlinux.h". (inspired by 'selftests' bpf_tracing_net.h)

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Link: https://lore.kernel.org/r/20230115071613.125791-8-danieltimlee@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>