Rename: primitives/sr-std -> primitives/sp-std (#4327)

* primitives/sr-std -> primitives/std

* fix

* fix conflict

* rstd -> sp-std

* git mv

* fix review

* fix merge

substrate/frame/contracts/src/gas.rs

@@ -15,7 +15,7 @@
 // along with Substrate. If not, see <http://www.gnu.org/licenses/>.
 
 use crate::{GasSpent, Module, Trait, BalanceOf, NegativeImbalanceOf};
-use rstd::convert::TryFrom;
+use sp_std::convert::TryFrom;
 use sp_runtime::traits::{
 	CheckedMul, Zero, SaturatedConversion, SimpleArithmetic, UniqueSaturatedInto,
 };