Administration: Pass the result of `set-screen-option` filter to the new...

Administration: Pass the result of `set-screen-option` filter to the new `set_screen_option_{$option}` filter to ensure backward compatibility.

Rename the `$keep` parameter of both filters to `$screen_option` for clarity, update the documentation to better reflect its purpose.

Props Chouby, sswells, SergeyBiryukov.
Fixes #50392.
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git-svn-id: https://core.svn.wordpress.org/trunk@48010 1a063a9b-81f0-0310-95a4-ce76da25c4cd