Enable backfilling cost tagging for AWS Openscapes account

[yuvipanda]

After #4473 is done, we will need to enable backfilling costs for the current month. There isn't much point enabling backfilling costs for much longer than that, because we have created new resources for a few things (EFS, nodegroups) that we can't trust values going back. So let's backfill it just for July.

https://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/cost-allocation-backfill.html describes how to request backfill through the web interface.

It may take ~1-2 days for this to complete.

Definition of done

• In the 'filter' options in the right sidebar of the AWS Cost Explorer allows filtering by all the tags specified in Enable cost allocation tags on openscapes AWS account #4473

[consideRatio]

• While Enable cost allocation tags on openscapes AWS account #4473 is done now, we should also await Add tags to EFS filesystems on openscapes cluster #4464 before doing this.

[consideRatio]

All of the tasks we waited for has been completed, backfilling task started successfully!

[consideRatio]

Success!