PHP-Flasher for toast messages (#13401)

* PHP-Flasher for toast messages
Allows customized template
removes dependency on unmaintained package using dev stability
no solution for javascript toasts yet

Use DI in places it makes sense

allow html in flashes

Use "template.librenms" as a default notification style

merge toast containers
toastr needs to be second because it will find the containr made by flasher, but the inverse is not true

upgrade php-flasher to add custom options and persistent notifications

Add dark theme

* update composer.lock

html/css/styles.css

@@ -2271,10 +2271,6 @@ label {
   width: auto !important;
 }
 
-.toast-top-right {
-  top: 34px;
-}
-
 .tooltip {
     display: block !important;
     z-index: 10000;