Add functions to sniff `Magento2.Functions.DiscouragedFunction` of the `magento-coding-standard`

[andrewbess]

Description (*)

The RFC proposes to deprecate the listed functionality in PHP 8.1 and remove it in PHP 9 - PHP RFC: Deprecations for PHP 8.1
We need to add deprecated functions into sniff Magento2.Functions.DiscouragedFunction for functions from RFC exclude of

• mb_check_encoding() without argument
• get_class(), get_parent_class() and get_called_class() without argument - if it needed

ToDo:
Fixed sniff Magento2.Functions.DiscouragedFunction in magento-codding-standard

[m2-assistant]

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[m2-assistant]

Hi @anzin. Thank you for working on this issue.
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[andrewbess]

Fixes have been delivered into magento-coding-standard