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

provisionerd/proto/version.go

@@ -44,9 +44,12 @@ import "github.com/coder/coder/v2/apiversion"
 //     -> `has_ai_tasks` in `CompleteJob.TemplateImport`
 //     -> `has_ai_tasks` and `ai_tasks` in `PlanComplete`
 //     -> new message types `AITaskSidebarApp` and `AITask`
+//
+// API v1.8:
+//   - Add new fields `description` and `icon` to `Preset`.
 const (
 	CurrentMajor = 1
-	CurrentMinor = 7
+	CurrentMinor = 8
 )
 
 // CurrentVersion is the current provisionerd API version.