simpleperf: fix parsing tracing format for fuzzer

Let ParseTracingField return std::nullopt when having parsing errors.
Let GetTracingFormatHavingId return std::nullopt instead of aborting
when can't find a matching one.

Bug: 291895810
Test: run libsimpleperf_report_fuzzer
Test: run simpleperf_unit_test
Test: run test.py

Change-Id: Ibb1f2b72c9113a5e529b948d488f3efe8045564b
7 files changed