fix(fargate): improve cloudwatch retention policy user facing logs

[bernardobridge]

Description

As seen in #2486, there might be missing permissions in the role being used to run artillery CLI, which would cause a confusing warning with a stack trace, despite the test continuing to run. This makes the warning message more easy to understanding.

The warning will look something like this now:

Launching workers... [11:58:44]
Waiting for Fargate... [11:58:45]
⠇ 
User: arn:aws:sts::ACCOUNT_ID:assumed-role/ROLE_NAME/SESSION_NAME is not authorized to perform: logs:PutRetentionPolicy on resource: arn:aws:logs:us-east-1:ACCOUNT_ID:log-group:artilleryio-log-group/artilleryio-cluster:log-stream: because no identity-based policy allows the logs:PutRetentionPolicy action

WARNING: Missing logs:PutRetentionPolicy permission to set Cloudwatch retention policy. Please ensure the IAM role has the necessary permissions:
https://www.artillery.io/docs/load-testing-at-scale/aws-fargate#iam-permissions
The test will resume without setting the retention policy.

Waiting for workers to start: pending: 1 [11:59:16]
Waiting for workers to start: pending: 1 [11:59:27]

Pre-merge checklist

This is for use by the Artillery team. Please leave this in if you're contributing to Artillery.

• Does this require an update to the docs?
• Does this require a changelog entry?