sp-api: `impl_runtime_apis!` replace the use of `Self` as a type argument (#4012)

closes #1890 

### Overview 

Introduces similar checker struct to `CheckTraitDecls` in
`decl_runtime_apis!` - `CheckTraitImpls`. Overrides
`visit::visit_type_path` to detect usage of `Self` as a type argument
within the scope of `impl_runtime_apis!`.

**Note**: only prevents the usage of `Self` as a type argument in an
angle bracket `<>`, as it is the only use case that fails to compile.
For example, the code
[below](https://github.com/paritytech/polkadot-sdk/blob/master/cumulus/parachains/runtimes/bridge-hubs/bridge-hub-westend/src/lib.rs#L1002)
compiles fine:

```rs
impl BridgeMessagesConfig<WithBridgeHubRococoMessagesInstance> for Runtime {
  fn is_relayer_rewarded(relayer: &Self::AccountId) -> bool {
	  let bench_lane_id = <Self as BridgeMessagesConfig<WithBridgeHubRococoMessagesInstance>>::bench_lane_id();
	  // ...
```

### Result

Given a block of code like this:

```rs
impl_runtime_apis! {
	impl apis::Core<Block> for Runtime {
		fn initialize_block(header: &HeaderFor<Self>) -> ExtrinsicInclusionMode {
			let _: HeaderFor<Self> = header.clone();
			RuntimeExecutive::initialize_block(header)
		}
		// ...
         }
// ...
```

<details open>

<summary>Output:</summary>

```bash
$ cargo build --release -p minimal-template-node
  error: `Self` can not be used as type argument in the scope of `impl_runtime_apis!`. Use `Runtime` instead.
     --> /polkadot-sdk/templates/minimal/runtime/src/lib.rs:133:11
      |
  133 |             let _: HeaderFor<Self> = header.clone();
      |                    ^^^^^^^^^^^^^^^

  error: `Self` can not be used as type argument in the scope of `impl_runtime_apis!`. Use `Runtime` instead.
     --> /polkadot-sdk/templates/minimal/runtime/src/lib.rs:132:32
      |
  132 |         fn initialize_block(header: &HeaderFor<Self>) -> ExtrinsicInclusionMode {
```

</details>

---------

Co-authored-by: Pavlo Khrystenko <[email protected]>
Co-authored-by: Pavlo Khrystenko <[email protected]>
Co-authored-by: Alexandru Vasile <[email protected]>
Co-authored-by: Bastian Köcher <[email protected]>