Custom LoggerFactory for log4cxx

FileLoggerFactory simply outputs logs to a single file.
If users want to rotate log files, they need to implement custom LoggerFactory by themselves.
Log4cxxLogger was deleted in #283, but this is useful for users.

So I would like to recover Log4cxxLogger.
I would not create specialized methods for Log4cxxLogger as there used to be, but would like to make it one of the options in the same category as ConsoleLoggerFactory and FileLoggerFactory.
https://github.com/apache/pulsar-client-cpp/pull/283/files#diff-abb02af9369945477ebc3329b299544ba67e214ac3f36c55b1f9e27f68469abf
If we want to avoid embedding it as a build option, we can separate the client and logger packages.

先檢視 #283 的 diff，以及目前的 ConsoleLoggerFactory 和 FileLoggerFactory 實作，以了解 logger 選項如何公開。在選擇內嵌的 build 選項或分開的 client/logger package 之前，先檢查 build 和 package 配置。完成的標準是將 Log4cxxLogger 恢復為同級選項，且使用者可以在不使用專用方法的情況下，利用它進行自訂 log rotation。

由索引模型根據 Issue 內容生成。