build: build fuzz tests by default.
This fixes issue #19388. The changes are as follows:
- Add a new flag to configure, --enable-fuzz-binary, which allows building test/fuzz/fuzz regardless of whether we are building to do actual fuzzing
- Set -DPROVIDE_MAIN_FUNCTION whenever --enable-fuzz is no
- Add the following libraries to FUZZ_SUITE_LD_COMMON:
- if necessary, some or all of:
- LIBBITCOIN_ZMQ / ZMQ_LIBS