fix: tune Besu options to work with tx_spammer (#612)

At startup Besu does not return a good gas price estimation (WIP to fix
this) and the default number of accepted connection is not enough to
sustain the tx_spammer, so this PR tune some options to allow to use the
tx_spammer wth Besu.

---------
Co-authored-by: Barnabas Busa <barnabas.busa@ethereum.org>

.github/tests/besu-all.yaml

 participants:
-  - el_type: geth
-    cl_type: teku
-  - el_type: geth
-    cl_type: teku
   - el_type: besu
     cl_type: prysm
+  - el_type: besu
+    cl_type: teku
   - el_type: besu
     cl_type: nimbus
   - el_type: besu
     cl_type: lighthouse
   - el_type: besu
     cl_type: lodestar
+  - el_type: besu
+    cl_type: grandine
 additional_services: []

src/el/besu/besu_launcher.star

@@ -207,6 +207,7 @@ def get_config(
         "--rpc-http-port={0}".format(RPC_PORT_NUM),
         "--rpc-http-api=ADMIN,CLIQUE,ETH,NET,DEBUG,TXPOOL,ENGINE,TRACE,WEB3",
         "--rpc-http-cors-origins=*",
+        "--rpc-http-max-active-connections=300",
         "--rpc-ws-enabled=true",
         "--rpc-ws-host=0.0.0.0",
         "--rpc-ws-port={0}".format(WS_PORT_NUM),
@@ -225,6 +226,7 @@ def get_config(
         "--metrics-enabled=true",
         "--metrics-host=0.0.0.0",
         "--metrics-port={0}".format(METRICS_PORT_NUM),
+        "--min-gas-price=1000000000",
     ]
     if (
         network not in constants.PUBLIC_NETWORKS