P4TC - Change header fields to network order in C Program

[komaljai]

Convert all header fields to network order in EBPF C Program. Handle corresponding arithmetic operations with respect to endianness in parser and control block.

[fruffy]

Byte order is a long-standing problem in the eBPF back end. https://github.com/p4lang/p4c/issues/1122

Does this PR address the issue? We may not even need to make the distinction between "TC" and eBPF then.

[komaljai]

Byte order is a long-standing problem in the eBPF back end. #1122

Does this PR address the issue? We may not even need to make the distinction between "TC" and eBPF then.

Thanks @fruffy for pointing the EBPF back-end open issue. This PR addresses the same issue, however due to several opens, have currently marked it as Draft.