large loop in yaml_parser_fetch_more_tokens

[nora-pxh]

In the current version (0.2.5) use the following file to run fuzz.
https://github.com/google/oss-fuzz/blob/master/projects/libyaml/libyaml_dumper_fuzzer.c

ALARM: working on the last Unit for 181 seconds
and the timeout value is 180 (use -timeout=N to change)
By the way, even if the timeout value is 600, the result is still the same.
==739722== ERROR: libFuzzer: timeout after 181 seconds
# 0 0x52aac1 in __sanitizer_print_stack_trace /src/llvm-project/compiler-rt/lib/asan/asan_stack.cpp:86:3
# 1 0x475568 in fuzzer::PrintStackTrace() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerUtil.cpp:210:5
# 2 0x459629 in fuzzer::Fuzzer::AlarmCallback() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:301:5
# 3 0x7fe8bc0024bf (/lib64/libpthread.so.0+0x134bf)
# 4 0x58debf in yaml_parser_stale_simple_keys /src/libyaml/src/scanner.c:1063:5
# 5 0x58e0ff in yaml_parser_fetch_next_token /src/libyaml/src/scanner.c:880:10
# 6 0x58dbbe in yaml_parser_fetch_more_tokens /src/libyaml/src/scanner.c:847:14
# 7 0x5703b4 in yaml_parser_parse_flow_mapping_key /src/libyaml/src/parser.c:1112:13
# 8 0x5677d0 in yaml_parser_state_machine /src/libyaml/src/parser.c:288:20
# 9 0x56749f in yaml_parser_parse /src/libyaml/src/parser.c:188:12
# 10 0x560d3a in yaml_parser_load_nodes /src/libyaml/src/loader.c:222:14
# 11 0x56091c in yaml_parser_load_document /src/libyaml/src/loader.c:203:10
# 12 0x5604c1 in yaml_parser_load /src/libyaml/src/loader.c:118:10
# 13 0x55780a in LLVMFuzzerTestOneInput /src/libyaml_dumper_fuzzer.c:237:10
# 14 0x45ae53 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:599:15
# 15 0x4465c2 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:323:6
# 16 0x44c28e in fuzzer::FuzzerDriver(int*, char***, int ()(unsigned char const, unsigned long)) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:856:9
# 17 0x475d42 in main /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerMain.cpp:20:10
# 18 0x7fe8bbe33b26 in __libc_start_main (/lib64/libc.so.6+0x25b26)
# 19 0x422069 in _start (/opt/oss-fuzz/build/out/libyaml/libyaml_dumper_fuzzer+0x422069)

DEDUP_TOKEN: __sanitizer_print_stack_trace--fuzzer::PrintStackTrace()--fuzzer::Fuzzer::AlarmCallback()
SUMMARY: libFuzzer: timeout