Allow options file to control LeakSanitizer

The options file can control ASAN, MSAN, UBSAN and libfuzzer options. However, there seems to be no way to set `LSAN_OPTIONS` -- these seem to be separate from ASAN. For example, ASAN has its own suppression option but doesn't recognize leaks, they need to be set separately via `LSAN_OPTIONS`.

Start by locating the options-file handling and the existing paths for ASAN_OPTIONS, MSAN_OPTIONS, UBSAN_OPTIONS, and libFuzzer options. Trace how those settings reach fuzzing runs, then verify that an LSAN_OPTIONS value is accepted and applied separately, including the suppression use case described in the issue.

Written by the indexing model from the issue text.