Incorrect encoding when predicate arguments in fold contain permission introspection

[Dev-XYS]

Related to #568.

The same bug occurs in fold statements as well.

field f: Int

predicate P(x: Ref, p: Perm)
{
    acc(x.f)
}

method foo(x: Ref)
    requires acc(x.f)
{
    fold P(x, perm(x.f))
    assert P(x, write)    // Verification fails.
}

Different to #568, the bug also affects permission introspection to heap locations in the predicate body, since Carbon first exhales predicate body before inhaling the predicate instance.