Enhance bigtable-beam-import project to import multiple hbase table snapshots into bigtable

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**Is your feature request related to a problem? Please describe.**
[Current Dataflow Pipeline](https://github.com/googleapis/java-bigtable-hbase/tree/main/bigtable-dataflow-parent/bigtable-beam-import) supports importing snapshot of only a single hbase table into BigTable.

**Describe the solution you'd like**
It would be helpful to enhance the pipeline to support following features:

- Importing multiple snapshots in the same pipeline into corresponding BigTable tables
- Handle parallelization of Skewed regions to enhance performance
- Configuring additional BigTable configuration

**Describe alternatives you've considered**
Run multiple copies of the pipeline for each snapshot

**Additional context**
NA