eth, les, params: log chain config a bit saner (#24904)

Previously on Geth startup we just logged the chain config is a semi-json-y format. Whilst that worked while we had a handful of hard-forks defined, currently it's kind of unwieldy. 

This PR converts that original data dump and converts it into a user friendly - alas multiline - log output.

tests/init.go

@@ -211,7 +211,7 @@ var Forks = map[string]*params.ChainConfig{
 		BerlinBlock:             big.NewInt(0),
 		LondonBlock:             big.NewInt(0),
 		ArrowGlacierBlock:       big.NewInt(0),
-		MergeForkBlock:          big.NewInt(0),
+		MergeNetsplitBlock:      big.NewInt(0),
 		TerminalTotalDifficulty: big.NewInt(0),
 	},
 }