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

provisionersdk/proto/provisioner.proto

@@ -101,6 +101,8 @@ message Preset {
   repeated PresetParameter parameters = 2;
   Prebuild prebuild = 3;
   bool default = 4;
+  string description = 5;
+  string icon = 6;
 }
 
 message PresetParameter {