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

codersdk/presets.go

@@ -16,6 +16,8 @@ type Preset struct {
 	Parameters               []PresetParameter
 	Default                  bool
 	DesiredPrebuildInstances *int
+	Description              string
+	Icon                     string
 }
 
 type PresetParameter struct {