Logger: combined key & cipher file

Use one single .ulge file to store both wrapped symmetric key and
encrypted ulog data instead of creating separate .ulgk/ulgc files

src/modules/logger/logger.cpp

@@ -1307,7 +1307,7 @@ int Logger::get_log_file_name(LogType type, char *file_name, size_t file_name_si
 #if defined(PX4_CRYPTO)
 
 	if (_param_sdlog_crypto_algorithm.get() != 0) {
-		crypto_suffix = "c";
+		crypto_suffix = "e";
 	}
 
 #endif