[Backport from polkadot-sdk] Move chain definitions to separate folder (#2892)

* [Bridges] Move chain definitions to separate folder (#3822)

Related to
https://github.com/paritytech/parity-bridges-common/issues/2538

This PR doesn't contain any functional changes.

The PR moves specific bridged chain definitions from
`bridges/primitives` to `bridges/chains` folder in order to facilitate
the migration of the `parity-bridges-repo` into `polkadot-sdk` as
discussed in https://hackmd.io/LprWjZ0bQXKpFeveYHIRXw?view

Apart from this it also includes some cosmetic changes to some
`Cargo.toml` files as a result of running `diener workspacify`.

(cherry picked from commit 0711729d25)

* diener workspacify

bridges/chains/chain-rococo/Cargo.toml

@@ -0,0 +1,35 @@
+[package]
+name = "bp-rococo"
+description = "Primitives of Rococo runtime."
+version = "0.6.0"
+authors.workspace = true
+edition.workspace = true
+license = "GPL-3.0-or-later WITH Classpath-exception-2.0"
+
+[lints]
+workspace = true
+
+[dependencies]
+
+# Bridge Dependencies
+
+bp-header-chain = { path = "../../primitives/header-chain", default-features = false }
+bp-polkadot-core = { path = "../../primitives/polkadot-core", default-features = false }
+bp-runtime = { path = "../../primitives/runtime", default-features = false }
+
+# Substrate Based Dependencies
+
+frame-support = { git = "https://github.com/paritytech/polkadot-sdk", branch = "master", default-features = false }
+sp-api = { git = "https://github.com/paritytech/polkadot-sdk", branch = "master", default-features = false }
+sp-std = { git = "https://github.com/paritytech/polkadot-sdk", branch = "master", default-features = false }
+
+[features]
+default = ["std"]
+std = [
+	"bp-header-chain/std",
+	"bp-polkadot-core/std",
+	"bp-runtime/std",
+	"frame-support/std",
+	"sp-api/std",
+	"sp-std/std",
+]