Remove primitives (#8057)

# Description

Removes the bridge-related primitives for Polkadot and Kusama from
/bridges/chains, to be moved into parity-bridges-common and
polkadot-fellows/runtimes, per [this
issue](polkadot-fellows/runtimes#627). Also
tweaks the readme and scripts to be more platform-agnostic.
**NB**: This will require those who run the bridge zombienet tests to
rename the zombienet binary from `zombienet-linux-x64` to just
`zombienet`.

## Integration

This update breaks parity-bridges-common's dependency on these
primitives, which are re-added to parity-bridge-common in [this
PR](paritytech/parity-bridges-common#3145).

Author: antkve

Cargo.lock

@@ -13,12 +13,8 @@ members = [
 	"bridges/chains/chain-asset-hub-rococo",
 	"bridges/chains/chain-asset-hub-westend",
 	"bridges/chains/chain-bridge-hub-cumulus",
-	"bridges/chains/chain-bridge-hub-kusama",
-	"bridges/chains/chain-bridge-hub-polkadot",
 	"bridges/chains/chain-bridge-hub-rococo",
 	"bridges/chains/chain-bridge-hub-westend",
-	"bridges/chains/chain-kusama",
-	"bridges/chains/chain-polkadot",
 	"bridges/chains/chain-polkadot-bulletin",
 	"bridges/chains/chain-rococo",
 	"bridges/chains/chain-westend",
@@ -660,15 +656,11 @@ bp-asset-hub-rococo = { path = "bridges/chains/chain-asset-hub-rococo", default-
 bp-asset-hub-westend = { path = "bridges/chains/chain-asset-hub-westend", default-features = false }
 bp-beefy = { path = "bridges/primitives/beefy", default-features = false }
 bp-bridge-hub-cumulus = { path = "bridges/chains/chain-bridge-hub-cumulus", default-features = false }
-bp-bridge-hub-kusama = { default-features = false, path = "bridges/chains/chain-bridge-hub-kusama" }
-bp-bridge-hub-polkadot = { path = "bridges/chains/chain-bridge-hub-polkadot", default-features = false }
 bp-bridge-hub-rococo = { path = "bridges/chains/chain-bridge-hub-rococo", default-features = false }
 bp-bridge-hub-westend = { path = "bridges/chains/chain-bridge-hub-westend", default-features = false }
 bp-header-chain = { path = "bridges/primitives/header-chain", default-features = false }
-bp-kusama = { default-features = false, path = "bridges/chains/chain-kusama" }
 bp-messages = { path = "bridges/primitives/messages", default-features = false }
 bp-parachains = { path = "bridges/primitives/parachains", default-features = false }
-bp-polkadot = { default-features = false, path = "bridges/chains/chain-polkadot" }
 bp-polkadot-bulletin = { path = "bridges/chains/chain-polkadot-bulletin", default-features = false }
 bp-polkadot-core = { path = "bridges/primitives/polkadot-core", default-features = false }
 bp-relayers = { path = "bridges/primitives/relayers", default-features = false }