tc / ebpf backends use unparsed annotations

[asl]

There should never be unparsed annotations actually used in the compiler -- it is just a matter of adding one PARSE_type line to parseAnnotations.cpp (or in a backend file). This is related to the mess that is "structured" annotations -- all annotations are structured -- it is just that some people didn't want to enumerate all the annotations in parseAnnotations.cpp as that was too hard to maintain.

Originally posted by @ChrisDodd in https://github.com/p4lang/p4c/pull/5018#discussion_r1841362778

[asl]

See https://github.com/p4lang/p4c/pull/5018/files#diff-2494735621545235a407b7a74124268ece6ec99bc8f55a5a581675771e3c0114R208