AWS: Create image AMI's task

[sparshev]

For caching purposes creating the modified root OS disk image could be much more efficient then storing cache in workspace snapshot due to lazy-read nature of the snapshots, where root disks are stored directly on EC2. Should not be that hard especially we already have implemented snapshot task.

Additionally need a way to allow to modify the label (even not the same one) with the updated image, but sounds too complicated for one task.

[sparshev]

Thought about what's more scary - to modify the label automatically or to allow to use tags to specify the image and chose second one. Will mark in the docs that it's not recommended - but if we rebuilding the image regularly - having a specific label to utilize the latest images by tag is something less invasive and complicated, even if it's making the label reproducibility harder.