### What changes were proposed in this pull request?
set params default values in trait ...Params in both Scala and Python.
I will do this in two PRs. I will change classification, regression, clustering and fpm in this PR. Will change the rest in another PR.
### Why are the changes needed?
Make ML has the same default param values between estimator and its corresponding transformer, and also between Scala and Python.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
Existing tests
Closes#29112 from huaxingao/set_default.
Authored-by: Huaxin Gao <huaxing@us.ibm.com>
Signed-off-by: Huaxin Gao <huaxing@us.ibm.com>