Size of Filter Control
Description
For the toolbar, search fields, pagination, etc. the values from data-icon-size are taken over. However, the filter control fields may have a different size.
https://live.bootstrap-table.com/code/sebastiangehrt/6450
Here, should btn-XX also be added for a consistent look.
Example with fix: https://live.bootstrap-table.com/code/djhvscf/9693
@djhvscf The class form-control is missing for the select, which cause in a other style of the inputs.
The form-control class is there:

The form-control class is there:
The form-control class (without -sm) of the select :-)

If I add the form-control class then the form-control-sm is not applied. I don't think we need form-control class when using form-control-{size}
For me it works fine, it is also needed.
Please check the bootstrap 4 documentation.

ok, let me review it
I think I'm going to remove this issue from the scope of https://github.com/wenzhixin/bootstrap-table/pull/5583 since the filter control extension does not work in other themes. @UtechtDustin @wenzhixin
See this issue for tracking purposes https://github.com/wenzhixin/bootstrap-table/issues/5968