feat: use preview to compute workspace tags from terraform (#18720)

If using dynamic parameters, workspace tags are extracted using
`coder/preview`.

enterprise/coderd/testdata/parameters/workspacetags/main.tf

@@ -0,0 +1,66 @@
+terraform {
+  required_providers {
+    coder = {
+      source = "coder/coder"
+    }
+  }
+}
+
+
+variable "stringvar" {
+  type    = string
+  default = "bar"
+}
+
+variable "numvar" {
+  type    = number
+  default = 42
+}
+
+variable "boolvar" {
+  type    = bool
+  default = true
+}
+
+data "coder_parameter" "stringparam" {
+  name    = "stringparam"
+  type    = "string"
+  default = "foo"
+}
+
+data "coder_parameter" "stringparamref" {
+  name    = "stringparamref"
+  type    = "string"
+  default = data.coder_parameter.stringparam.value
+}
+
+data "coder_parameter" "numparam" {
+  name    = "numparam"
+  type    = "number"
+  default = 7
+}
+
+data "coder_parameter" "boolparam" {
+  name    = "boolparam"
+  type    = "bool"
+  default = true
+}
+
+data "coder_parameter" "listparam" {
+  name    = "listparam"
+  type    = "list(string)"
+  default = jsonencode(["a", "b"])
+}
+
+data "coder_workspace_tags" "tags" {
+  tags = {
+    "function"    = format("param is %s", data.coder_parameter.stringparamref.value)
+    "stringvar"   = var.stringvar
+    "numvar"      = var.numvar
+    "boolvar"     = var.boolvar
+    "stringparam" = data.coder_parameter.stringparam.value
+    "numparam"    = data.coder_parameter.numparam.value
+    "boolparam"   = data.coder_parameter.boolparam.value
+    "listparam"   = data.coder_parameter.listparam.value
+  }
+}