test: remove confusing MAX_BLOCK_BASE_SIZE

The constant `MAX_BLOCK_BASE_SIZE` has been removed from the
core implementation years ago due to being confusing and
superfluous, as it is implied by the block weight limit (see
PRs #10618 and #10608). Since there is also no point in
still keeping it in the functional test framework, we switch
to weight-based accounting on the relevant test code parts
and use `MAX_BLOCK_WEIGHT` instead for the block limit
checks.

test/functional/mempool_accept.py

@@ -14,7 +14,7 @@ from test_framework.messages import (
     COIN,
     COutPoint,
     CTxOut,
-    MAX_BLOCK_BASE_SIZE,
+    MAX_BLOCK_WEIGHT,
     MAX_MONEY,
     tx_from_hex,
 )
@@ -207,7 +207,7 @@ class MempoolAcceptanceTest(BitcoinTestFramework):
 
         self.log.info('A really large transaction')
         tx = tx_from_hex(raw_tx_reference)
-        tx.vin = [tx.vin[0]] * math.ceil(MAX_BLOCK_BASE_SIZE / len(tx.vin[0].serialize()))
+        tx.vin = [tx.vin[0]] * math.ceil(MAX_BLOCK_WEIGHT // 4 / len(tx.vin[0].serialize()))
         self.check_mempool_result(
             result_expected=[{'txid': tx.rehash(), 'allowed': False, 'reject-reason': 'bad-txns-oversize'}],
             rawtxs=[tx.serialize().hex()],