Add MSK Cluster Volume Auto Scaling Support

[jinayvora1990]

https://docs.aws.amazon.com/msk/latest/developerguide/msk-autoexpand.html

Add options in module to expand MSK cluster storage by specifying auto scaling policy with storage utilisation target and max storage capacity.

[tomek-cz]

It's be great to support it. Can we at least add a support for the storage size to be ignored, if we implement storage resizing outside of this module? Otherwise applying shows the mismatch between the storage (that auto-grew) and the storage size in the code, and it tries to shrink the storage (which fails, as you cannot shrink it). Allowing the storage size changes to be ignored (on the module level) will help here.