(cli): remove quiet flag from SdkProvider.forEnvironment

[mrgrain]

SdkProvider.forEnvironment has a quiet flag which seems to only exist for the integration with cdk-assets.
This is the only one place that flag is used to set it to a different value than the default:
https://github.com/aws/aws-cdk/blob/5178050dc318fb0dc643bc208af553adb8245bc5/packages/aws-cdk/lib/util/asset-publishing.ts

The flag itself is the same that is passed to cdk-assets, so we only can do this once cdklabs/cdk-assets#196 is completed.

We don't want flags to be passed around. Instead everything is always logged with the same log level and the logger than decides if a message needs printing or not.

Expected Behavior

All output is always "logged" with a log level.
Use the log level as defined by the CLI.

Current Behavior

Output is logged or not depending on the flag.