Migrate loading spinners

Migrate loading spinners to be
design system compliant using
loading icon helper.

Changelog: changed

app/views/ide/_show.html.haml

@@ -9,5 +9,5 @@
 
 #ide.ide-loading{ data: ide_data }
   .text-center
-    .gl-spinner.gl-spinner-md
+    = gl_loading_icon(size: 'md')
     %h2.clgray= _('Loading the GitLab IDE...')

app/views/projects/_activity.html.haml

@@ -11,4 +11,4 @@
 
 .content_list.project-activity{ :"data-href" => activity_project_path(@project) }
 .loading
-  .gl-spinner.gl-spinner-md
+  = gl_loading_icon(size: 'md')

app/views/projects/network/show.html.haml

@@ -16,5 +16,4 @@
 
     - if @commit
       .network-graph.gl-bg-white.gl-overflow-scroll.gl-overflow-x-hidden{ data: { url: @url, commit_url: @commit_url, ref: @ref, commit_id: @commit.id } }
-        .text-center.gl-mt-3
-          .gl-spinner.gl-spinner-md
+        = gl_loading_icon(size: 'md', css_class: 'gl-mt-3')

ee/app/views/projects/_project_templates.html.haml

@@ -18,11 +18,9 @@
     .project-templates-buttons.import-buttons.tab-pane.active#built-in
       = render partial: 'projects/project_templates/template', collection: Gitlab::ProjectTemplate.all + Gitlab::SampleDataTemplate.all
     .project-templates-buttons.import-buttons.tab-pane.js-custom-instance-project-templates-tab-content#custom-instance-project-templates{ data: {initial_templates: user_available_project_templates_path(current_user)} }
-      .text-center.m-4
-        .gl-spinner.gl-spinner-md
+      = gl_loading_icon(size: 'md', css_class: 'gl-mt-4')
     .project-templates-buttons.import-buttons.tab-pane.js-custom-group-project-templates-tab-content#custom-group-project-templates{ data: {initial_templates: user_available_group_templates_path(current_user, group_id: group_id)} }
-      .text-center.m-4
-        .gl-spinner.gl-spinner-md
+      = gl_loading_icon(size: 'md', css_class: 'gl-mt-4')
 
   .project-fields-form
     = render 'projects/project_templates/project_fields_form'