Aws plan percistence: rename env variable to be more explicit

[motatoes]

Current env variable for AWS plan percistence is AWS_S3_BUCKET. Should be renamed to something more explicity like AWS_S3_ARTEFACT_BUCKET to match the gcp naming convention.

[Pushkarmondal]

Hey @motatoes can I work on this issue?

[NikhilKalloli]

Hey @motatoes Can you be more specific on where can I update AWS_S3_BUCKET to AWS_S3_ARTEFACT_BUCKET because I can't find any env variable named as AWS_S3_BUCKET