Update Sodium Compat to 1.18.0

[jrf]

Sodium_Compat 1.18.0 has just been released and includes some improvements, including a new feature which will also be included in PHP 8.2.

The version included with WP should be updated.

Full details:

• ​https://github.com/paragonie/sodium_compat/releases/tag/v1.18.0
• ​https://github.com/paragonie/sodium_compat/compare/v1.17.1...v1.18.0

I've reviewed the diff and would recommend an update at the earliest convenience.

Previously: #48371, #51399, #51925, #53274, #53907, #55453
Related: #54730

[SergeyBiryukov]

In 54150:

Upgrade/Install: Update sodium_compat to v1.18.0.

The latest version of sodium_compat includes some improvements, as well as a new feature which will also be included in PHP 8.2.

• Fixed issues with the PHP autoloader:
  • ​#145: For WordPress, this ensures when Ed25519 is included, so too is the class it inherits from.
  • ​#148, ​#149: For PHP 7.4+ with opcache preloading, this ensures the include guards don't fail.
• ​#144: Added sodium_crypto_stream_xchacha20_xor_ic()
  • See ​pull request for php-src (merged in PHP 8.2)
  • For motivation: ​paragonie/halite#178

Release notes:
​https://github.com/paragonie/sodium_compat/releases/tag/v1.18.0

A full list of changes in this update can be found on GitHub:
​https://github.com/paragonie/sodium_compat/compare/v1.17.1...v1.18.0

Follow-up to [49741], [51002], [51591], [52988].

Props jrf, paragoninitiativeenterprises.
Fixes #56564.