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>

Cargo.lock

@@ -2153,6 +2153,7 @@ dependencies = [
  "static_assertions",
  "substrate-wasm-builder",
  "testnet-parachains-constants",
+ "tuplex",
 ]
 
 [[package]]
@@ -2311,6 +2312,7 @@ dependencies = [
  "static_assertions",
  "substrate-wasm-builder",
  "testnet-parachains-constants",
+ "tuplex",
  "westend-runtime-constants",
 ]
 
@@ -2349,6 +2351,7 @@ dependencies = [
  "staging-xcm",
  "staging-xcm-builder",
  "static_assertions",
+ "tuplex",
 ]
 
 [[package]]
@@ -22046,6 +22049,12 @@ dependencies = [
  "utf-8",
 ]
 
+[[package]]
+name = "tuplex"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "676ac81d5454c4dcf37955d34fa8626ede3490f744b86ca14a7b90168d2a08aa"
+
 [[package]]
 name = "twox-hash"
 version = "1.6.3"