[Upgrade]: Modernize existing sniffs

[gmazzap]

Description of the bug

Currently many existing sniffs does not support modern features like Enum.

We need to make sure all sniffs work well with all the PHP 8+ features.

Moreover, there are conditions that exists due to support of PHP 7.3-, for exmple void return type is enforced conditionally if PHP 7.1+ is supported.
Because now we have PHP 7.4 we can reduce the complexity of sniffs removing those now unnecessary conditions.

Reproduction instructions

N/A

Expected behavior

All sniff should take into account PHP 8+ features.
All sniff should remove support for PHP 7.3-

Environment info

No response

Relevant log output

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Additional context

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