Options: Prevent unnecessary SQL updates by `update_option`.

Previously an option containing an object would trigger an SQL `UPDATE` on all calls to `update_option`, even if the old and new values were identical. This was due to the old and new values having differing resource IDs.

This change compares the old and new values as serialized data to remove the resource ID from the comparison.

Props salcode, bradyvercher, peterwilsoncc.
Fixes #38903.

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git-svn-id: https://core.svn.wordpress.org/trunk@39504 1a063a9b-81f0-0310-95a4-ce76da25c4cd