Fix smidge bundles not always invalidated between backoffice versions. (#11700)

* Introduced new smidge CacheBuster with sensible defaults.

* Bring back reset functionality in SmidgeRuntimeMinifier

* Clearer obsolete messaging.

src/Umbraco.Core/Configuration/EntryAssemblyMetadata.cs

@@ -0,0 +1,24 @@
+using System.Reflection;
+
+namespace Umbraco.Cms.Core.Configuration
+{
+    internal class EntryAssemblyMetadata : IEntryAssemblyMetadata
+    {
+        public EntryAssemblyMetadata()
+        {
+            var entryAssembly = Assembly.GetEntryAssembly();
+
+            Name = entryAssembly
+                ?.GetName()
+                ?.Name ?? string.Empty;
+
+            InformationalVersion = entryAssembly
+                ?.GetCustomAttribute<AssemblyInformationalVersionAttribute>()
+                ?.InformationalVersion ?? string.Empty;
+        }
+
+        public string Name { get; }
+
+        public string InformationalVersion { get; }
+    }
+}