Add comprehensive logging to libmongocrypt.

Some background:

• drivers that use libmongocrypt can set a log callback to receive log messages (using this public API).
• right now we only log things with log level MONGOCRYPT_LOG_LEVEL_TRACE, using a convenience macro CRYPT_TRACEF.
• we should log all input arguments and output arguments of all public API (anything defined in mongocrypt.h), probably with MONGOCRYPT_LOG_LEVEL_INFO.
• for a mongocrypt_binary_t, how we log it depends on what it stores. If it represents BSON, we convert it to a bson_t first, and print the BSON representation with something like bson_as_json.
• consider anything else worth logging. If it turns out we don't need all five log levels, we could consider removing some.