feat: support icon and description in preset (#18977)

## Description 

This PR adds support for `description` and `icon` fields to
`template_version_presets`. These fields will allow displaying richer
information for presets in the UI, improving the user experience when
creating a workspace.
Both fields are optional, non-nullable, and default to empty strings.

## Changes

* Database migration with the addition of `description VARCHAR(128)` and
`icon VARCHAR(256)` columns to the `template_version_presets` table.
* Updated the `CreateWorkspacePageView` in the UI

Note: UI changes will be addressed in a separate PR

coderd/database/queries/presets.sql

@@ -7,7 +7,9 @@ INSERT INTO template_version_presets (
 	desired_instances,
 	invalidate_after_secs,
 	scheduling_timezone,
-	is_default
+	is_default,
+	description,
+	icon
 )
 VALUES (
 	@id,
@@ -17,7 +19,9 @@ VALUES (
 	@desired_instances,
 	@invalidate_after_secs,
 	@scheduling_timezone,
-	@is_default
+	@is_default,
+	@description,
+	@icon
 ) RETURNING *;
 
 -- name: InsertPresetParameters :many