node,blocksync,config: remove support for running nodes with blocksync disabled (#7159)

We stopped testing these configurations a while ago, and it doesn't
really make sense to allow nodes to run in this configuration. This
drops support for non-blocksync nodes and cleans up the
configuration/tests accordingly.

Closes: #6908

test/e2e/generator/generate_test.go

@@ -43,9 +43,6 @@ func TestGenerator(t *testing.T) {
 						t.Run("PrivvalProtocol", func(t *testing.T) {
 							require.NotZero(t, node.PrivvalProtocol)
 						})
-						t.Run("BlockSync", func(t *testing.T) {
-							require.NotZero(t, node.BlockSync)
-						})
 					}
 				})
 			}