Rename WP_Comments_List_Table::comment_status_dropdown() to ::comment_type_dropdown()

[SergeyBiryukov]

Background: #40188, #50815.

[48521] introduced a method for displaying a comment type drop-down for filtering on the Comments list table.

For some reason, the method is called ::comment_status_dropdown(), despite not having anything to do with a comment status. This can be confusing now and problematic when working on tickets like #20977 in the future.

I propose renaming the method to ::comment_type_dropdown() for clarity. It's marked as protected, so there should not be any backward compatibility concerns.

[SergeyBiryukov]

In 48943:

Comments: Rename WP_Comments_List_Table::comment_status_dropdown() to ::comment_type_dropdown().

This better reflects the purpose of the method, which doesn't have anything to do with a comment status.

Follow-up to [48521].

Props davidbaumwald, johnbillion, SergeyBiryukov.
Fixes #51248.