Revert "journalctl: honour --output-fields= in -o cat mode"

[evverx]

Reverts #15648

@keszybz CIFuzz is failing with

AddressSanitizer:DEADLYSIGNAL
=================================================================
==16==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7f864f98948e bp 0x7ffde5c6b7c0 sp 0x7ffde5c6b560 T0)
==16==The signal is caused by a READ memory access.
==16==Hint: address points to the zero page.
SCARINESS: 10 (null-deref)
    #0 0x7f864f98948e in output_short /work/build/../../src/systemd/src/shared/logs-show.c
    #1 0x7f864f984624 in show_journal_entry /work/build/../../src/systemd/src/shared/logs-show.c:1154:15
    #2 0x7f864f984b63 in show_journal /work/build/../../src/systemd/src/shared/logs-show.c:1239:21
    #3 0x4cabab in LLVMFuzzerTestOneInput /work/build/../../src/systemd/src/fuzz/fuzz-journal-remote.c:67:21
    #4 0x51fd16 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/libfuzzer/FuzzerLoop.cpp:556:15
    #5 0x51c330 in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool*) /src/libfuzzer/FuzzerLoop.cpp:470:3
    #6 0x523700 in fuzzer::Fuzzer::ReadAndExecuteSeedCorpora(std::__1::vector<fuzzer::SizedFile, fuzzer::fuzzer_allocator<fuzzer::SizedFile> >&) /src/libfuzzer/FuzzerLoop.cpp:765:7
    #7 0x5246cd in fuzzer::Fuzzer::Loop(std::__1::vector<fuzzer::SizedFile, fuzzer::fuzzer_allocator<fuzzer::SizedFile> >&) /src/libfuzzer/FuzzerLoop.cpp:792:3
    #8 0x4de3d1 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /src/libfuzzer/FuzzerDriver.cpp:824:6
    #9 0x4cfb47 in main /src/libfuzzer/FuzzerMain.cpp:19:10
    #10 0x7f864e69782f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
    #11 0x41f2a8 in _start (out/fuzz-journal-remote+0x41f2a8)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /work/build/../../src/systemd/src/shared/logs-show.c in output_short
==16==ABORTING
MS: 0 ; base unit: 0000000000000000000000000000000000000000
0x44,0x3d,0xa,0x5f,0x5f,0x52,0x45,0x41,0x4c,0x54,0x49,0x4d,0x45,0x5f,0x54,0x49,0x4d,0x45,0x53,0x54,0x41,0x4d,0x50,0x3d,0x31,0xa,0xa,
D=\x0a__REALTIME_TIMESTAMP=1\x0a\x0a
artifact_prefix='./'; Test unit written to ./crash-d635b9dd31cceff3c912fd45e1a58d7e90f0ad73
Base64: RD0KX19SRUFMVElNRV9USU1FU1RBTVA9MQoK

[poettering]

hmm it's the second part of that PR that causes this I guess. Should suffice to reert that. i.e. apparently a function parameter using static array sizes also means that it is not nullable anymore... Would be good if we could somehow denote parameters as "either of size 2 or null"...

[evverx]

hmm it's the second part of that PR that causes this I guess. Should suffice to reert that.

@poettering agreed. "static" is incompatible with null pointers and once #15704 is merged it should be easier to catch issues like that. But I'm away from my laptop so unfortunately I can't seem to revert commits selectively by just pressing the "revert" button on GitHub. If someone else could revert only the last commit it would be great.