Add support for namespaced functions in `FullyQualifiedStrictTypesFixer`

Feature request

Hmm, it seems that this fixer can't work with functions at all. I see that this fixer doesn't import functions at all right now.

It would be great to be able to import namespaced functions using this fixer.

Link to Discussion where feature request was formed

https://github.com/PHP-CS-Fixer/PHP-CS-Fixer/pull/9350#discussion_r2698405757

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