test: add missing assert_equal imports

The later scripted diff only rewrites call sites.
Add `assert_equal` imports in the remaining files that still need them so the mechanical replacement can apply cleanly.

test/functional/test_framework/crypto/ellswift.py

@@ -13,6 +13,7 @@ import random
 import unittest
 
 from test_framework.crypto.secp256k1 import FE, G, GE
+from test_framework.util import assert_equal
 
 # Precomputed constant square root of -3 (mod p).
 MINUS_3_SQRT = FE(-3).sqrt()

test/functional/test_framework/crypto/secp256k1.py

@@ -17,7 +17,7 @@ Exports:
 
 import unittest
 from hashlib import sha256
-from test_framework.util import assert_not_equal
+from test_framework.util import assert_equal, assert_not_equal
 
 class FE:
     """Objects of this class represent elements of the field GF(2**256 - 2**32 - 977).

test/functional/test_framework/key.py

@@ -14,7 +14,7 @@ import random
 import unittest
 
 from test_framework.crypto import secp256k1
-from test_framework.util import assert_not_equal, random_bitflip
+from test_framework.util import assert_equal, assert_not_equal, random_bitflip
 
 # Point with no known discrete log.
 H_POINT = "50929b74c1a04954b78b4b6035e97a5e078a5a0f28ec96d547bfee9ace803ac0"

test/functional/test_framework/psbt.py

@@ -5,6 +5,7 @@
 
 import base64
 
+from .util import assert_equal
 from .messages import (
     CTransaction,
     deser_string,