Fix nostd build of several crates (#4060)

Preparation for https://github.com/paritytech/polkadot-sdk/pull/3935

Changes:
- Add some `default-features = false` for the case that a crate and that
dependency both support nostd builds.
- Shuffle files around of some benchmarking-only crates. These
conditionally disabled the `cfg_attr` for nostd and pulled in libstd.
Example [here](https://github.com/ggwpez/zepter/pull/95). The actual
logic is moved into a `inner.rs` to preserve nostd capability of the
crate in case the benchmarking feature is disabled.
- Add some `use sp_std::vec` where needed.
- Remove some `optional = true` in cases where it was not optional.
- Removed one superfluous `cfg_attr(not(feature = "std"), no_std..`.

All in all this should be logical no-op.

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

cumulus/primitives/parachain-inherent/Cargo.toml

@@ -17,8 +17,8 @@ scale-info = { version = "2.11.1", default-features = false, features = ["derive
 # Substrate
 sp-core = { path = "../../../substrate/primitives/core", default-features = false }
 sp-inherents = { path = "../../../substrate/primitives/inherents", default-features = false }
-sp-runtime = { path = "../../../substrate/primitives/runtime", optional = true }
-sp-state-machine = { path = "../../../substrate/primitives/state-machine", optional = true }
+sp-runtime = { path = "../../../substrate/primitives/runtime", optional = true, default-features = false }
+sp-state-machine = { path = "../../../substrate/primitives/state-machine", optional = true, default-features = false }
 sp-std = { path = "../../../substrate/primitives/std", default-features = false }
 sp-trie = { path = "../../../substrate/primitives/trie", default-features = false }
 
@@ -34,6 +34,8 @@ std = [
 	"scale-info/std",
 	"sp-core/std",
 	"sp-inherents/std",
+	"sp-runtime?/std",
+	"sp-state-machine?/std",
 	"sp-std/std",
 	"sp-trie/std",
 ]