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/dbfake/dbfake.go

@@ -417,6 +417,8 @@ func (t TemplateVersionBuilder) Do() TemplateVersionResponse {
 			InvalidateAfterSecs: preset.InvalidateAfterSecs,
 			SchedulingTimezone:  preset.SchedulingTimezone,
 			IsDefault:           false,
+			Description:         preset.Description,
+			Icon:                preset.Icon,
 		})
 	}