chore: refactor time.Duration -> int64 milliseconds for FE consumption (#1944)

* Changes all public-facing codersdk types to use a plain int64 (milliseconds) instead of time.Duration.
* Makes autostart_schedule a *string as it may not be present.
* Adds a utils/ptr package with some useful methods.

examples/templates/aws-linux/main.tf

@@ -33,7 +33,7 @@ variable "region" {
   description = "What region should your workspace live in?"
   default     = "us-east-1"
   validation {
-    condition     = contains([
+    condition = contains([
       "ap-northeast-1",
       "ap-northeast-2",
       "ap-northeast-3",