[SPARK-3397] Bump pom.xml version number of master branch to 1.2.0-SNAPSHOT

Author: GuoQiang Li <witgo@qq.com>

Closes #2268 from witgo/SPARK-3397 and squashes the following commits:

eaf913f [GuoQiang Li] Bump pom.xml version number of master branch to 1.2.0-SNAPSHOT
[SPARK-3273][SPARK-3301]We should read the version information from the same place

Author: GuoQiang Li <witgo@qq.com>

Closes #2175 from witgo/SPARK-3273 and squashes the following commits:

cf9c65a [GuoQiang Li] We should read the version information from the same place
2a44e2f [GuoQiang Li] The spark version in the welcome message of pyspark is not correct