tka: compact TKA storage on startup

Signed-off-by: Tom DNetto <tom@tailscale.com>

ipn/ipnlocal/local.go

@@ -4740,6 +4740,9 @@ func (b *LocalBackend) initTKALocked() error {
 		if err != nil {
 			return fmt.Errorf("initializing tka: %v", err)
 		}
+		if err := authority.Compact(storage, tkaCompactionDefaults); err != nil {
+			b.logf("tka compaction failed: %v", err)
+		}
 
 		b.tka = &tkaState{
 			profile:   cp.ID,