Improve security key handling in pluggable.php

[spacedmonkey]

Requires #61053.

Use wp_prime_site_option_caches to prime option / network option caches if not defined as const.

Trac ticket: https://core.trac.wordpress.org/ticket/59871

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Props spacedmonkey.

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[peterwilsoncc]

@spacedmonkey It looks like you accidentally pushed to the WordPress org's copy of the repo. Are you able to reopen from your fork so the branch doesn't get deleted when the bots sync every minute or so.

[spacedmonkey]

@spacedmonkey It looks like you accidentally pushed to the WordPress org's copy of the repo. Are you able to reopen from your fork so the branch doesn't get deleted when the bots sync every minute or so.

Done #6597