Add two new zombienet tests for bridges (manual run) (#3072)

extracted useful code from #2982 

This PR:
- adds test 2 for Rococo <> Westend bridge: checks that relayer doesn't
submit any extra headers while there are no any messages;
- adds test 3 for Rococo <> Westend bridge: checks that relayer doesn't
submit any extra headers when there are messages;
- fixes most of comments from #2439 (like: log names, ability to run
specify test number when calling `run-tests.sh`).

Right now of all our tests, only test 2 is working (until BHs will be
upgraded to use async backing), so you can test it with
`./bridges/zombienet/run-tests.sh --test 2` locally.

cumulus/scripts/bridges_common.sh

@@ -48,6 +48,14 @@ function ensure_polkadot_js_api() {
     fi
 }
 
+function call_polkadot_js_api() {
+    # --noWait: without that argument `polkadot-js-api` waits until transaction is included into the block.
+    #           With it, it just submits it to the tx pool and exits.
+    # --nonce -1: means to compute transaction nonce using `system_accountNextIndex` RPC, which includes all
+    #             transaction that are in the tx pool.
+    polkadot-js-api --noWait --nonce -1 "$@"
+}
+
 function generate_hex_encoded_call_data() {
     local type=$1
     local endpoint=$2
@@ -80,7 +88,7 @@ function transfer_balance() {
     echo "      amount: ${amount}"
     echo "--------------------------------------------------"
 
-    polkadot-js-api \
+    call_polkadot_js_api \
         --ws "${runtime_para_endpoint}" \
         --seed "${seed?}" \
         tx.balances.transferAllowDeath \
@@ -145,7 +153,7 @@ function send_governance_transact() {
     echo ""
     echo "--------------------------------------------------"
 
-    polkadot-js-api \
+    call_polkadot_js_api \
         --ws "${relay_url?}" \
         --seed "${relay_chain_seed?}" \
         --sudo \
@@ -170,7 +178,7 @@ function open_hrmp_channels() {
     echo "      max_message_size: ${max_message_size}"
     echo "      params:"
     echo "--------------------------------------------------"
-    polkadot-js-api \
+    call_polkadot_js_api \
         --ws "${relay_url?}" \
         --seed "${relay_chain_seed?}" \
         --sudo \
@@ -254,7 +262,7 @@ function limited_reserve_transfer_assets() {
     echo ""
     echo "--------------------------------------------------"
 
-    polkadot-js-api \
+    call_polkadot_js_api \
         --ws "${url?}" \
         --seed "${seed?}" \
         tx.polkadotXcm.limitedReserveTransferAssets \
@@ -293,7 +301,7 @@ function claim_rewards() {
     echo "${rewards_account_params}"
     echo "--------------------------------------------------"
 
-    polkadot-js-api \
+    call_polkadot_js_api \
         --ws "${runtime_para_endpoint}" \
         --seed "${seed?}" \
         tx.bridgeRelayers.claimRewards \