Bridge: make some headers submissions free (#4102)

supersedes https://github.com/paritytech/parity-bridges-common/pull/2873

Draft because of couple of TODOs:
- [x] fix remaining TODOs;
- [x] double check that all changes from
https://github.com/paritytech/parity-bridges-common/pull/2873 are
correctly ported;
- [x] create a separate PR (on top of that one or a follow up?) for
https://github.com/paritytech/polkadot-sdk/tree/sv-try-new-bridge-fees;
- [x] fix compilation issues (haven't checked, but there should be
many).

---------

Co-authored-by: Adrian Catangiu <adrian@parity.io>

bridges/testing/environments/rococo-westend/helper.sh

@@ -1,3 +1,9 @@
 #!/bin/bash
 
-$ENV_PATH/bridges_rococo_westend.sh "$@"
+if [ $1 == "auto-log" ]; then
+    shift # ignore "auto-log"
+    log_name=$1
+    $ENV_PATH/bridges_rococo_westend.sh "$@" >$TEST_DIR/logs/$log_name.log
+else
+    $ENV_PATH/bridges_rococo_westend.sh "$@"
+fi