This adopts the full networking stack from lighthouse

Code is adopted from lighthouse, which is licensed under Apache-2. Unfortunately
because the dependencies we use are different, it's not possible to directly
depend on upstream.

So that we're on a version that supports gossipsub, thanks to lighthouse.

This copies blockchain-network-libp2p crate as the foundation to continue to
build upon.

beacon-wasm: use the builtin serde feature provided by wasm-bindgen

beacon, beacon-wasm: fix incorrect example block and remove f64 parsing for uint

wasm: fix U1099511627776 exceeding u32 limit

dep: update bm-le to 0.10

beacon-wasm: webassembly-compiled beacon state transition function

srml-casper: introduce epoch number

srml-casper: implement slashing conditions

Casper consensus in SRML