Build each language fuzzer in two modes (halt_on_error=true and
halt_on_error=false) and use different timeouts for each fuzzer.
Also merge the run-fuzzer and reproduce scripts so they use identical
values of ASAN_OPTIONS/UBSAN_OPTIONS/etc0
This adds support for fuzzing tree-sitter grammars with libFuzzer. This
currently only works on Linux because of linking issues on macOS. Breifly, the
AddressSanitizer library is dynamically linked into the fuzzer binary and
cannot be found at runtime if built with a compiler that wasn't provided by
Xcode(?). The runtime library is statically linked on Linux so this isn't a
problem.
