With `ivy_check trace=true` output variables in alphabetical order

[plredmond]

When printing out variables in the ivy_check trace=true output, this change makes variables print in alphabetical order. This is helpful since all the nested structures are output at the same level with . delimited paths in their names, making it hard to locate a single nested structure when the output is not sorted.

Before

searching for a small model... done
[
    0:index < 0 = false
    pid.iter.val(0) = 0
    vc.kv.end(0) = 0
    vc.repr(0) = 0
    0:index = 0
    index.succ(0,0) = false
    pid.iter.is_end(0) = true
    vc.kv.key_at(0,0,0) = false
]

The nested structures pid.iter.* and vc.kv.* aren't obvious.

After

searching for a small model... done
[
    0:index < 0 = false
    0:index = 0
    index.succ(0,0) = false
    pid.iter.is_end(0) = true
    pid.iter.val(0) = 0
    vc.kv.end(0) = 0
    vc.kv.key_at(0,0,0) = false
    vc.repr(0) = 0
]

Both nested structures' properties are grouped together.

cc @nano-o