UI: Consistently calculate BitNode "level" (#2645)

src/BitNode/BitNodeUtils.ts

@@ -93,3 +93,12 @@ export function finishBitNode() {
   }
   wd.backdoorInstalled = true;
 }
+
+/**
+ * BitNode level is not something that is stored, but rather calculated from the current BN and SF level. The concept
+ * appeared because saying "Enter BN1.2" is shorter than saying "Enter BN1 with SF1.1". This is how we display it in the
+ * BitVerse UI and other places. This function is used to consistently calculate this "level".
+ */
+export function getBitNodeLevel(bn = Player.bitNodeN, sfLevel = Player.activeSourceFileLvl(bn)): number {
+  return Math.min(sfLevel + 1, bn === 12 ? Number.MAX_VALUE : 3);
+}