[Improvement] Support env.sh and add HADOOP_CONF_DIR and HIVE_CONF_DIR to CLASSPATH

[baiyangtx]

Why are the changes needed?

HiveConf can load the existing hive-site.xml from the classpath during initialization.

So Amoro should support adding some directories to the classpath at startup.

In addition, user-defined environment variable configuration files need to be supported.

Brief change log

• Add a env.sh in ${AMORO_CONF_DIR}
• If exists env variables HADOOP_CONF_DIR and HIVE_CONF_DIR, add them to CLASSPATH
• Support add additional directories by env variable AMORO_ADDITION_CLASSPATH.
• Print all env variables and their value at startup.

How was this patch tested?

• Add some test cases that check the changes thoroughly including negative and positive cases if possible

• Add screenshots for manual tests if appropriate

• Run test locally before making a pull request

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not documented)

[huyuanfeng2018]

If we can export hadoop's classpath, do we still need to package the hadoop client into amoro?