Fix docs on Alicloud builder
Fix docs on Alicloud builder

- Fix the link to instance types page.
- Disk configurations should go into `image_disk_mappings` array.
- If `io_optimized` is not set, it's always `false`. (NOT inferred by instance type)
tb3088/packer,rnaveiras/packer,ricardclau/packer,mitchellh/packer,mitchellh/packer,mkuzmin/packer,timsutton/packer,pieter-lazzaro/packer,timsutton/packer,bryson/packer,hashicorp/packer,ricardclau/packer,ricardclau/packer,dave2/packer,rnaveiras/packer,tb3088/packer,tas50/packer,hashicorp/packer,timsutton/packer,rnaveiras/packer,paulmey/packer,grubernaut/packer,tas50/packer,bryson/packer,bryson/packer,grubernaut/packer,ChrisLundquist/packer,hashicorp/packer,grubernaut/packer,paulmey/packer,mkuzmin/packer,paulmey/packer,tb3088/packer,rnaveiras/packer,dave2/packer,dave2/packer,youhong316/packer,mitchellh/packer,pecigonzalo/packer,KohlsTechnology/packer,rnaveiras/packer,ChrisLundquist/packer,dave2/packer,mitchellh/packer,KohlsTechnology/packer,youhong316/packer,tb3088/packer,ricardclau/packer,rnaveiras/packer,grubernaut/packer,youhong316/packer,ChrisLundquist/packer,hashicorp/packer,mitchellh/packer,KohlsTechnology/packer,grubernaut/packer,timsutton/packer,tas50/packer,pieter-lazzaro/packer,ChrisLundquist/packer,KohlsTechnology/packer,youhong316/packer,paulmey/packer,paulmey/packer,youhong316/packer,ChrisLundquist/packer,dave2/packer,youhong316/packer,pieter-lazzaro/packer,timsutton/packer,pieter-lazzaro/packer,grubernaut/packer,bryson/packer,tb3088/packer,tas50/packer,pecigonzalo/packer,KohlsTechnology/packer,tas50/packer,pecigonzalo/packer,bryson/packer,timsutton/packer,pecigonzalo/packer,ricardclau/packer,ChrisLundquist/packer,dave2/packer,tas50/packer,pieter-lazzaro/packer,KohlsTechnology/packer,paulmey/packer,tb3088/packer,bryson/packer,pieter-lazzaro/packer,mkuzmin/packer,mkuzmin/packer,ricardclau/packer,mkuzmin/packer,mkuzmin/packer