Allow adding/updating provisioner tags on templates via terraform

[matifali]

We should Allow adding/updating tags from Terraform to allow controlling them as IaC. Currently, it's only possible via API, CLI, or UI.

Originally posted by @matifali in #6442 (comment)

[matifali]

Can we consider this closed as #5979 is completed. Docs are here: https://coder.com/docs/templates/workspace-tags
cc: @johnstcn

[johnstcn]

@matifali #5979 is slightly different. Template tags are still a separate entity.

[matifali]

Hmm. Ok but with #5979 we can update the tags per workspace using terraform.
My original issue actually requested this and #5979 provides an alternative solution to it.

I agree that we still have template tags if someone isn't using the new coder_workspace_tags data source to update them per workspace.

[johnstcn]

Let's track this as part of #9948