Fix wallet_send.py wallet setup to work with descriptors

Fixes the wallet setup so this test works with descriptor wallets. Also
enabled explicit descriptor and legacy wallet testing in the test
runner.

test/functional/test_runner.py

@@ -252,7 +252,8 @@ BASE_SCRIPTS = [
     'rpc_estimatefee.py',
     'rpc_getblockstats.py',
     'wallet_create_tx.py --legacy-wallet',
-    'wallet_send.py',
+    'wallet_send.py --legacy-wallet',
+    'wallet_send.py --descriptors',
     'wallet_create_tx.py --descriptors',
     'p2p_fingerprint.py',
     'feature_uacomment.py',