Allow more non-inline modules in blocks
Currently, non-inline modules without a `#[path]` attribute are not allowed in blocks.
This PR allows non-inline modules that have an ancestor module with a `#[path]` attribute, provided there is not a nearer ancestor block.
For example,
```rust
fn main() {
#[path = "..."] mod foo {
mod bar; //< allowed by this PR
fn f() {
mod bar; //< still an error
}
}
}
```
Fixes#36772.
r? @nikomatsakis
f1ea5cc273