Switch default EMR on EC2 instance types to m7g

[ctas582]

Some performance testing of the bulk import approaches has yielded the following results. 10B randomly generated records, with a simple schema (key:string, timestamp:int64, value:string), were ingested from 160 Parquet files with zstd compression, with a total size of ~175.5 GB.

The tests show that Graviton based m7g instances are faster and cheaper than the current default instance types (m7i).