Add support for importing resources

[tlindsay42]

Users should be able to import existing HCX instances. In my case, I had an HCX deployment for VMware Cloud on AWS take an unusually long amount of time to complete and the apply failed. Went to try and import, and found that I couldn't. Tried to rerun apply for the two, and got the following error:

Plan: 2 to add, 0 to change, 0 to destroy.

Do you want to perform these actions?
  Terraform will perform the actions described above.
  Only 'yes' will be accepted to approve.

  Enter a value: yes

hcx_vmc.hcx_sddc_b: Creating...
hcx_vmc.hcx_sddc_a: Creating...

Error: Already activated



Error: Already activated

Trying to undeploy now and will apply again. [fingers crossed]

[tlindsay42]

https://www.terraform.io/docs/extend/resources/import.html