New metric filtering missed blocks

[twoeths]

Is your feature request related to a problem? Please describe.

In Prater, from Apr 08, seems like there are some validators send late gossip blocks, these blocks are missed blocks but it make our chart looks really urgly

One example is as below, the gossip block is sent almost 2 minutes after the slot started

Apr-15 08:58:15.844[NETWORK]       verbose: Received gossip block slot=2791482, root=0x4250…57ee, curentSlot=2791491, peerId=bafzaajiiaijccawxi3dft7goz4wuf6ugdy7j4s5ymjisbiwqxu6ddj7llhyg3tdsge, delaySec=111.80999994277954

and it's marked as missed in beaconcha.in

Describe the solution you'd like

Create new metric to track "new chain head" block delay second