Prepare UI tests for Rust 1.51 & new CI image (#8474)

* Prepare UI tests for Rust 1.51 & new CI image

* another stderr to be fixed

Co-authored-by: Denis P <denis.pisarev@parity.io>

substrate/frame/support/test/tests/construct_runtime_ui/missing_system_module.stderr

@@ -1,7 +1,6 @@
 error: `System` pallet declaration is missing. Please add this line: `System: frame_system::{Pallet, Call, Storage, Config, Event<T>},`
  --> $DIR/missing_system_module.rs:8:2
   |
-8 |       {
-  |  _____^
+8 | /     {
 9 | |     }
   | |_____^

substrate/frame/support/test/tests/derive_no_bound_ui/eq.stderr

@@ -4,4 +4,9 @@ error[E0277]: can't compare `Foo<T>` with `Foo<T>`
 6   | struct Foo<T: Config> {
     |        ^^^ no implementation for `Foo<T> == Foo<T>`
     |
+   ::: $RUST/core/src/cmp.rs
+    |
+    | pub trait Eq: PartialEq<Self> {
+    |               --------------- required by this bound in `Eq`
+    |
     = help: the trait `PartialEq` is not implemented for `Foo<T>`

substrate/frame/support/test/tests/pallet_ui/hooks_invalid_item.stderr

@@ -1,5 +1,15 @@
-error[E0107]: wrong number of type arguments: expected 1, found 0
-  --> $DIR/hooks_invalid_item.rs:12:18
-   |
-12 |     impl<T: Config> Hooks for Pallet<T> {}
-   |                     ^^^^^ expected 1 type argument
+error[E0107]: missing generics for trait `Hooks`
+   --> $DIR/hooks_invalid_item.rs:12:18
+    |
+12  |     impl<T: Config> Hooks for Pallet<T> {}
+    |                     ^^^^^ expected 1 type argument
+    |
+note: trait defined here, with 1 type parameter: `BlockNumber`
+   --> $DIR/hooks.rs:206:11
+    |
+206 | pub trait Hooks<BlockNumber> {
+    |           ^^^^^ -----------
+help: use angle brackets to add missing type argument
+    |
+12  |     impl<T: Config> Hooks<BlockNumber> for Pallet<T> {}
+    |                          ^^^^^^^^^^^^^