feat(import): add script tool for multiple hbase snapshot imports)

[tianlei2]

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b/429250716

This is the second PR with the shell tool script. This a child of #4600, so the only file that needs to be reviewed is the script itself (bigtable-dataflow-parent/bigtable-beam-import/run-snapshot-import.sh). If this looks ok, I will merge this with the parent PR.

The script is originally from https://docs.google.com/document/d/1T7BQF-AYY8xGbdbhwkV7zPA11A_Fh5SRjA_7nkzeTos/edit?tab=t.twzz7rrh6jz7#heading=h.m7p3xy7m76u2

[vermas2012]

This is good, but how are we passing the restorePath?

[vermas2012]

I feel like we should have a custom restore path and the script (idempoent by adding timestamp etc) and use it for restore the path and pass it as the restorepath in every job.

Also, with this model, who cleans up the restore path? is there a way to trigger a cleanup at the end of the script? or we have a tool that can be used? We can also say its a manual step. but then this script should output something to the tune of "the snapshot was imported, please cleanup $RESTORE_PATH once validation succeeds."

[tianlei2]

Added some output for manual cleanups and passing restore path to every job.

[vermas2012]

In this model, how does the shard1. know htat it has to wait for restore to finish from shard 0? won't it run and fail becuase restore path is empty?

[tianlei2]

updating this to run a restore-only command first