Implemented PSG-680 - Sessions overview security recommendations

- remove uppercased strings from localizables
- moved inactivity computation to the service

Riot/Assets/Images.xcassets/DeviceManager/user_sessions_inactive.imageset/Contents.json

@@ -0,0 +1,12 @@
+{
+  "images" : [
+    {
+      "filename" : "user_sessions_inactive.svg",
+      "idiom" : "universal"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

Riot/Assets/Images.xcassets/DeviceManager/user_sessions_inactive.imageset/user_sessions_inactive.svg

@@ -0,0 +1,11 @@
+<svg width="32" height="32" viewBox="0 0 32 32" fill="none" xmlns="http://www.w3.org/2000/svg">
+<rect width="32" height="32" rx="8" fill="#F4F6FA"/>
+<g clip-path="url(#clip0_1002_97918)">
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+</g>
+<defs>
+<clipPath id="clip0_1002_97918">
+<rect width="16" height="16" fill="white" transform="translate(8 8)"/>
+</clipPath>
+</defs>
+</svg>