feat(virtsecrets): the secrets page on Bootstrap's cards, tables and dialogs

- One searchable card: each secret's type, usage and UUID, whether it is
  kept on disk or in memory and private, and the VMs and pools that use it,
  linked. A row menu sets its value or deletes it; Delete is disabled while
  the secret is in use, and its confirmation says what is not checked.
- One Set value dialog for every secret; its label and help follow the
  type (Ceph key, CHAP password, passphrase), and it says a new passphrase
  does not encrypt anew what the old one encrypted.
- New secret dialog: the usage's and value's labels and help follow the
  type; the value is optional; Private and Ephemeral are switches with help.

static/icon_cache/hdd-stack_None_None_None.svg

@@ -0,0 +1,14 @@
+<?xml version="1.0" ?>
+<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" class="bi bi-hdd-stack" viewBox="0 0 16 16">
+	
+  
+	<path d="M14 10a1 1 0 0 1 1 1v1a1 1 0 0 1-1 1H2a1 1 0 0 1-1-1v-1a1 1 0 0 1 1-1zM2 9a2 2 0 0 0-2 2v1a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2v-1a2 2 0 0 0-2-2z"/>
+	
+  
+	<path d="M5 11.5a.5.5 0 1 1-1 0 .5.5 0 0 1 1 0m-2 0a.5.5 0 1 1-1 0 .5.5 0 0 1 1 0M14 3a1 1 0 0 1 1 1v1a1 1 0 0 1-1 1H2a1 1 0 0 1-1-1V4a1 1 0 0 1 1-1zM2 2a2 2 0 0 0-2 2v1a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V4a2 2 0 0 0-2-2z"/>
+	
+  
+	<path d="M5 4.5a.5.5 0 1 1-1 0 .5.5 0 0 1 1 0m-2 0a.5.5 0 1 1-1 0 .5.5 0 0 1 1 0"/>
+	
+
+</svg>