break sp-api dependency cycle (#4352)

* move benches into tests, ignore non-passing doctests

* Rename sr-api folder

* Move test-primitives to primitives, use that for sp-api doctests

substrate/primitives/api/test/tests/ui/adding_self_parameter.stderr

@@ -0,0 +1,5 @@
+error: `self` as argument not supported.
+ --> $DIR/adding_self_parameter.rs:3:11
+  |
+3 |         fn test(&self);
+  |                 ^