### What changes were proposed in this pull request?
use `lazy array` instead of `var` for auxiliary variables in binary lor
### Why are the changes needed?
In https://github.com/apache/spark/pull/29255, I made a mistake:
the `private var _threshold` and `_rawThreshold` are initialized by defaut values of `threshold`, that is beacuse:
1, param `threshold` is set default value at first;
2, `_threshold` and `_rawThreshold` are initialized based on the default value;
3, param `threshold` is updated by the value from estimator, by `copyValues` method:
```
if (map.contains(param) && to.hasParam(param.name)) {
to.set(param.name, map(param))
}
```
We can update `_threshold` and `_rawThreshold` in `setThreshold` and `setThresholds`, but we can not update them in `set`/`copyValues` so their values are kept until methods `setThreshold` and `setThresholds` are called.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
test in repl
Closes#30013 from zhengruifeng/lor_threshold_init.
Authored-by: zhengruifeng <ruifengz@foxmail.com>
Signed-off-by: zhengruifeng <ruifengz@foxmail.com>
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