* Expose JSON_USE_EXCEPTION and JSON_HAS_INT64 as Bazel config flags with defaults that match the existing Bazel build.
Switch //:jsoncpp from using copts ro defines for JSON_USE_EXCEPTION and JSON_HAS_INT64 so that rules that depend on it get the same config.
Make src/test_lib_json/fuzz.cpp respect JSON_USE_EXCEPTION.
* #ifdef stuff that should only be used with JSON_USE_EXCEPTION.
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Co-authored-by: Jordan Bayles <bayles.jordan@gmail.com>