sim: add bootstrap test

Add caps for bootstrap option and implement simple bootstrap test
for the simulator.

Signed-off-by: Fabio Utzig <fabio.utzig@nordicsemi.no>
diff --git a/sim/src/caps.rs b/sim/src/caps.rs
index edffd0c..1d9a612 100644
--- a/sim/src/caps.rs
+++ b/sim/src/caps.rs
@@ -24,6 +24,7 @@
     SwapUsingMove        = (1 << 11),
     DowngradePrevention  = (1 << 12),
     EncX25519            = (1 << 13),
+    Bootstrap            = (1 << 14),
 }
 
 impl Caps {