Only prime salt options early once

[joemcgill]

Warning

This is pushed for testing purposes, currently is incomplete.

This adds a check to see if wp_salt() related options have already been primed before attempting to prime them again. This is necessary because the wp_salt() function can be called multiple times during the bootstrap process, and we need to ensure that the options are only primed once.

This also avoids an error that can occur if the salt related constants are defined after the first time wp_salt() is called, in which case the salt will not be present in the $duplicated_keys array.

Trac ticket: https://core.trac.wordpress.org/ticket/62424

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Props joemcgill.

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[github-actions]

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