Performance regression in `findall` on `Bool` array with predicate

Repro:

```jl
using BenchmarkTools
const y = rand(Bool, 1000)
@btime findall(x -> x > 1, y)
```

1.6:

```jl
julia> @btime findall(x -> x > 1, y)
  300.167 ns (1 allocation: 80 bytes)
Int64[]
```

1.7:

```jl
julia> @btime findall(x -> x > 1, y)
  702.505 ns (6 allocations: 4.50 KiB)
Int64[]
```

Also, note the increase in allocations
