[4.0] GMP system info

[brianteeman]

As webauthn plugin uses the php GMP extension it made sense to add a check for this in the system info.

There is already code that handles the error message #29731 this is just for the system info list.

Perhaps it should be added to the preinstall/preupdate checks as well as a recommendation (not required) @wilsonge @zero-24

/administrator/index.php?option=com_admin&view=sysinfo

[Quy]

I have tested this item ✅ successfully on fdac7b8

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[toivo]

I have tested this item ✅ successfully on fdac7b8

Tested successfully in Beta8-dev of 3 February using PHP 8.0.1.

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[brianteeman]

To be clear as I obviously wasnt explaining myself correctly.

If my proposal to use extension_loaded to determine if gmp is enabled in php is not suitable then dont we also have to correct all the other places where extension_loaded is used for the same thing. Otherwise all the comments about not being able to accurately determine if the extension is available using this method make all the existing tests invalid as well. Or is there something special about gmp that means it can't be tested in the same way as gd, zlib, xlib and mbstring.

Its very confusing because the php documentation says to do it this way https://www.php.net/manual/en/function.extension-loaded.php

[SharkyKZ]

This PR is fine for what it is.