feat(coderd/notifications): improve notification format consistency (#14967)

This Pull request addresses the more trivial items in
https://github.com/coder/coder/issues/14893.
These were simple formatting changes that I was able to fix despite
limited context.

Some more changes are required for which I will have to dig a bit deeper
into how the template contexts are populated. I'm happy to add those to
this PR or create a subsequent PR.

coderd/provisionerdserver/provisionerdserver.go

@@ -1128,6 +1128,7 @@ func (s *server) notifyWorkspaceManualBuildFailed(ctx context.Context, workspace
 			map[string]string{
 				"name":                     workspace.Name,
 				"template_name":            template.Name,
+				"template_display_name":    template.DisplayName,
 				"template_version_name":    templateVersion.Name,
 				"initiator":                build.InitiatorByUsername,
 				"workspace_owner_username": workspaceOwner.Username,