Read Bigtable Rows by Prefix

BigtableIO.Read provides a withKeyRange method to specify Bigtable keys within a [start, end) range. Unfortunately, it doesn't seem to provide a way of reading rows by a common prefix, although Bigtable natively supports this feature:  [https://cloud.google.com/bigtable/docs/cbt-reference#read_rows.](start, end) range. Unfortunately, it doesn't seem to provide a way of reading rows by a common prefix, although Bigtable natively supports this feature:  [https://cloud.google.com/bigtable/docs/cbt-reference#read_rows.)

Our use case, we have several "types" in our table, and each type is prefixed with the name of the type. The only other way to reading all rows with a specific prefix seems to use a RowFilter with row_key_regex_filter set, but it looks like that will result in a full table scan.

Imported from Jira [BEAM-10279](https://issues.apache.org/jira/browse/BEAM-10279). Original Jira may contain additional context.
Reported by: rafi_kamal.