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

provisioner/terraform/resources.go

@@ -965,7 +965,9 @@ func ConvertState(ctx context.Context, modules []*tfjson.StateModule, rawGraph s
 				ExpirationPolicy: expirationPolicy,
 				Scheduling:       scheduling,
 			},
-			Default: preset.Default,
+			Default:     preset.Default,
+			Description: preset.Description,
+			Icon:        preset.Icon,
 		}
 
 		if slice.Contains(duplicatedPresetNames, preset.Name) {