fix(pcapng): Journal Export entries with an unterminated binary field or a bare key do not rebuild byte-exactly #1413

Describe the bug
#1406's strict ruling covers a Journal Export binary field whose declared length overruns the entry, and #1412 fixes that case. Two neighbouring malformations still don't round-trip:

• a binary field whose length equals the available octets but has no closing \n;
• a bare KEY with no = and no newline.

To Reproduce
Run PCAPNG.from_data(PCAPNG(raw).info).data on #1412's head 0514d5c30. main behaves the same.

• BIN\n + <len=4> + abc\n, with no final terminator: 28 octets in, 32 out (a terminator is appended).
• A block holding only KEY: 16 octets in, 12 out (the entry is dropped).

Expected behavior
Per #1406's ruling, keep the whole entry raw and rebuild it verbatim.

Found by the #1412 cross-review, and I reproduced both. Blocked until #1412 merges.