Shift networking configuration (#4426)

## Issue Addressed
Addresses [#4401](https://github.com/sigp/lighthouse/issues/4401)

## Proposed Changes
Shift some constants into ```ChainSpec``` and remove the constant values from code space.

## Additional Info

I mostly used ```MainnetEthSpec::default_spec()``` for getting ```ChainSpec```. I wonder Did I make a mistake about that.


Co-authored-by: armaganyildirak <armaganyildirak@gmail.com>
Co-authored-by: Paul Hauner <paul@paulhauner.com>
Co-authored-by: Age Manning <Age@AgeManning.com>
Co-authored-by: Diva M <divma@protonmail.com>

beacon_node/client/src/builder.rs

@@ -795,7 +795,8 @@ where
                     self.work_reprocessing_rx,
                     None,
                     beacon_chain.slot_clock.clone(),
-                );
+                    beacon_chain.spec.maximum_gossip_clock_disparity(),
+                )?;
             }
 
             let state_advance_context = runtime_context.service_context("state_advance".into());