Add BigTable sink in Depot

[MayurGubrele]

Summary
As part of this feature, we want to add support for Google’s Bigtable sink in Depot.

Tasks

• Implement Bigtable sink with batching with the hardcoded key in the depot
• Add input to column - family - qualifier mapping support
• Define RowKey template and implement RowKeyTemplateParser
• Error parser and error handling for bigtable sink
• Capture Bigtable metrics and add instrumentation(logging and monitoring)
• Add dashboard panels to capture BigTable sink metrics
• Documentation for bigtable sink