Better track trailing commas in match arms. Do not suggest adding trailing comma to match arm with block body. Better heuristic for "is this match in one line".

When encountering an unreachable match arm, (correctly) suggest removing the entire arm:

```
error: a never pattern is always unreachable
  --> $DIR/ICE-130779-never-arm-no-oatherwise-block.rs:10:20
   |
LL |         Some(!) if true => {}
   |                            ^^ this will never be executed
   |
help: remove the unreachable match arm
   |
LL -         Some(!) if true => {}
LL +         Some(!),
   |
```

Noticed in rust-lang#137343 (comment).

```
error[E0004]: non-exhaustive patterns: `u8::MAX` not covered
  --> $DIR/exhaustiveness.rs:47:8
   |
LL |     m!(0u8, 0..255);
   |        ^^^ pattern `u8::MAX` not covered
   |
   = note: the matched value is of type `u8`
note: within macro `m`, this `match` expression doesn't expand to cover all patterns
  --> $DIR/exhaustiveness.rs:7:9
   |
LL | / macro_rules! m {
LL | |     ($s:expr, $($t:tt)+) => {
LL | |         match $s { $($t)+ => {} }
   | |         ^^^^^^^^^^^^^^^^^^^^^^^^^
LL | |     }
LL | | }
   | |_-
   = help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern
```

Parentheses surrounding patterns are not ketp in the HIR (and are warned against in the AST). In order to avoid having some suggestions break, we keep the outer span (including parentheses) when lowering the patterns.

```
error: a never pattern is always unreachable
  --> $DIR/ICE-133117-duplicate-never-arm.rs:9:26
   |
LL |         (!|!) if true => {}
   |                          ^^ this will never be executed
   |
help: remove the match arm expression
   |
LL -         (!|!) if true => {}
LL +         (!|!),
   |
```
```
error[E0308]: mismatched types
  --> $DIR/well-typed-edition-2024.rs:135:15
   |
LL |     let [&mut &(mut x)] = &mut [&0];
   |               ^^^^^^^^    --------- this expression has type `&mut [&{integer}; 1]`
   |               |
   |               expected integer, found `&_`
   |
   = note:   expected type `{integer}`
           found reference `&_`
help: consider removing `&` from the pattern
   |
LL -     let [&mut &(mut x)] = &mut [&0];
LL +     let [&mut (mut x)] = &mut [&0];
   |
```

```
error: a never pattern is always unreachable
  --> $DIR/pattern-behind-macro.rs:13:21
   |
LL |         never!() => {}
   |                     ^^ this will never be executed
   |
help: remove the match arm expression
   |
LL -         never!() => {}
LL +         never!(),
   |
```

Look up the macro backtrace call sites to see if we find where the macro was used as a pattern, to properly suggest removing match arm guard and body.