[lldb] Fix evaluating expressions without JIT in an object context (#145599)

If a server does not support allocating memory in an inferior process or
when debugging a core file, evaluating an expression in the context of a
value object results in an error:

```
error: <lldb wrapper prefix>:43:1: use of undeclared identifier '$__lldb_class'
   43 | $__lldb_class::$__lldb_expr(void *$__lldb_arg)
      | ^
```

Such expressions require a live address to be stored in the value
object. However, `EntityResultVariable::Dematerialize()` only sets
`ret->m_live_sp` if JIT is available, even if the address points to the
process memory and no custom allocations were made. Similarly,
`EntityPersistentVariable::Dematerialize()` tries to deallocate memory
based on the same check, resulting in an error if the memory was not
previously allocated in `EntityPersistentVariable::Materialize()`.

As an unintended bonus, the patch also fixes a FIXME case in
`TestCxxChar8_t.py`.