feat: support aggregate functions

[pnadolny13]

Currently if stats is used in the query then we throw an exception

tap-cloudwatch/tap_cloudwatch/cloudwatch_api.py

Line 94 in c83a222

if "stats" in query:

. Ideally we'd allow stats by disabling some of the other features that dont work with it.

• allow stats in query config, probably set a flag so other methods know stats is in use
• if stats is in query we might not need to force "@timestamp" to be there too because the aggregate might be messed up. So we'll need to deactivate incremental syncs for this case.
• Figure out how to handle schema generation. We hard code the log ID as the PK but could make that configurable
• I dont think we can paginate in batches so if we detect that the 10k batch limit is reached after aggregating then we need to throw and error

https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/CWL_QuerySyntax.html