[flang] Misleading diagnostic order for coarray declaration: "expected entity declarations" precedes "expected '::'"

### Summary

When a type-declaration statement has an attribute list followed by a misplaced
token, flang emits two recovery diagnostics — `expected '::'` and
`expected entity declarations` — but reports `expected entity declarations`
first. With an attribute list present, the `::` separator is required by the
standard (F2018 R801 / C801), so `expected '::'` is the accurate, actionable
diagnostic and should be the leading message.

### Reproducer

```fortran
subroutine s1(a)
real, dimension (:)[10] :: a
end subroutine
```

(The `[10]` coarray codimension is misplaced within the `DIMENSION` attribute.)

### Actual output

```
error: expected entity declarations
real, dimension (:)[10] :: a
^
error: expected '::'
real, dimension (:)[10] :: a
^
```

Note how `expected entity declarations` is listed first.

### Expected output

`expected '::'` should be reported first, since after the attribute list the
standard requires the `::` separator before the entity-declaration list.
`expected entity declarations` is not valid at that position without a
preceding `::`, so it should not be the primary message.

### Notes

- The set of emitted errors is otherwise correct; only the ordering / primary
message is wrong.
- This affects every declaration of the form `, ... `.
- This re-ordering of errors is a regression caused by https://github.com/llvm/llvm-project/pull/215886

Assisted-by: Claude Opus 4.8