feat: enable enterprise users to specify a custom logo (#5566)

* feat: enable enterprise users to specify a custom logo

This adds a field in deployment settings that allows users to specify
the URL to a custom logo that will display in the dashboard.

This also groups service banner into a new appearance settings page.
It adds a Fieldset component to allow for modular fields moving forward.

* Fix tests

codersdk/branding.go

@@ -0,0 +1,23 @@
+package codersdk
+
+import (
+	"context"
+	"net/http"
+)
+
+type UpdateBrandingRequest struct {
+	LogoURL string `json:"logo_url"`
+}
+
+// UpdateBranding applies customization settings available to Enterprise customers.
+func (c *Client) UpdateBranding(ctx context.Context, req UpdateBrandingRequest) error {
+	res, err := c.Request(ctx, http.MethodPut, "/api/v2/branding", req)
+	if err != nil {
+		return err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusOK {
+		return readBodyAsError(res)
+	}
+	return nil
+}