Compare empty blocks for equality based on tokens
fixes: #1390
This only considers empty blocks for now, though we should also catch something like this:
```rust
match 0 {
0 => {
do_something();
trace!(0);
0
}
1 => {
do_something();
trace!(1);
1
}
x => x,
}
```
As far as I can tell there aren't any negative effects on other lints. These blocks only happen to be the same for a given compilation, not all compilations.
changelog: Fix `match_on_same_arms` and others. Only consider empty blocks equal if the tokens contained are the same.
7be3a32f25