Rename all module.utils to module._utils (#1641)

* Rename all `module.utils` to `module._utils`

* fix imports to use _utils

Author: rayrapetyan

eth/beacon/utils/__init__.py renamed to eth/_utils/__init__.py

@@ -3,7 +3,7 @@
 from eth_hash.auto import keccak
 from eth_typing import Address
 
-from eth.utils.numeric import (
+from eth._utils.numeric import (
     int_to_bytes32,
 )
 

eth/utils/address.py renamed to eth/_utils/address.py

@@ -13,10 +13,10 @@
     ValidationError,
 )
 
-from eth.utils.padding import (
+from eth._utils.padding import (
     zpad_right,
 )
-from eth.utils.merkle import (
+from eth._utils.merkle import (
     calc_merkle_root,
 )
 

eth/utils/bitfield.py renamed to eth/_utils/bitfield.py

@@ -31,7 +31,7 @@
     curve_order,
     final_exponentiate
 )
-from eth.beacon.utils.hash import hash_eth2
+from eth.beacon._utils.hash import hash_eth2
 
 
 G2_cofactor = 305502333931268344200999753193121504214466019254188142667664032982267604182971884026507427359259977847832272839041616661285803823378372096355777062779109  # noqa: E501