Vectorize `@ inbounds for x in A ...`

This would previously have been an infinite loop if
`length(A) == typemax(Int)` so the loop vectorizer couldn't compute a
trip count.

(cherry picked from commit fa89a6e)
ref #13866

Currently, if a vector is resized in the midst of iteration, then `done` might "miss" the end of iteration. This trivially changes the definition to catch such a case. I am not sure what guarantees we make about mutating iterables during iteration, but this seems simple and easy to support.  Note, though, that it is somewhat tricky: until #13866 we used `i > length(a)`, but that foils vectorization due to the `typemax` case. This definition seems to get the best of both worlds. For a definition like `f` below, this new definition just requires one extra `add i64` operation in the preamble (before the loop). Everything else is identical to master.

```julia
function f(A)
    r = 0
    @inbounds for x in A
        r += x
    end
    r
end
```

Currently, if a vector is resized in the midst of iteration, then `done` might "miss" the end of iteration. This trivially changes the definition to catch such a case. I am not sure what guarantees we make about mutating iterables during iteration, but this seems simple and easy to support.  Note, though, that it is somewhat tricky: until #13866 we used `i > length(a)`, but that foils vectorization due to the `typemax` case. This definition seems to get the best of both worlds. For a definition like `f` below, this new definition just requires one extra `add i64` operation in the preamble (before the loop). Everything else is identical to master.

```julia
function f(A)
    r = 0
    @inbounds for x in A
        r += x
    end
    r
end
```

* More robust iteration over Vectors

Currently, if a vector is resized in the midst of iteration, then `done` might "miss" the end of iteration. This trivially changes the definition to catch such a case. I am not sure what guarantees we make about mutating iterables during iteration, but this seems simple and easy to support.  Note, though, that it is somewhat tricky: until #13866 we used `i > length(a)`, but that foils vectorization due to the `typemax` case. This definition seems to get the best of both worlds. For a definition like `f` below, this new definition just requires one extra `add i64` operation in the preamble (before the loop). Everything else is identical to master.

```julia
function f(A)
    r = 0
    @inbounds for x in A
        r += x
    end
    r
end
```