Update Sodium Compat to 1.19.0

[jrf]

Sodium_Compat 1.19.0 has just been released and includes improved compatibility with the PHP 8.0 named parameters functionality.
While WP itself can not use this functionality yet, plugins can, so this is a welcome improvement.

The version included with WP should be updated.

Full details:

• ​https://github.com/paragonie/sodium_compat/releases/tag/v1.19.0
• ​https://github.com/paragonie/sodium_compat/compare/v1.18.0...v1.19.0

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

Previously: #48371, #51399, #51925, #53274, #53907, #55453, #56564, #56642

Related: #51553, #55327, #55650

[SergeyBiryukov]

In 54310:

Upgrade/Install: Update sodium_compat to v1.19.0.

The latest version of sodium_compat includes improved compatibility with the PHP 8.0 named parameters functionality.

Release notes:
​https://github.com/paragonie/sodium_compat/releases/tag/v1.19.0

A full list of changes in this update can be found on GitHub:
​https://github.com/paragonie/sodium_compat/compare/v1.18.0...v1.19.0

Follow-up to [49741], [51002], [51591], [52988], [54150].

Props jrf, paragoninitiativeenterprises.
Fixes #56653.