bump libgmp requirement to avoid bug in 6.2.0

[1ma]

The reason I added a new lib-gmp section instead of setting a version in ext-gmp is because composer sees ext-gmp with the version of PHP you have installed, whereas lib-gmp show the actual version of libgmp installed in the system.

$ composer info -p | grep gmp
ext-gmp                8.3.14   The gmp PHP extension
lib-gmp                6.2.1    The gmp library

Sanity check. Momentarily setting lib-gmp to an unreleased version of libgmp yields this (correct) error:

$ composer install
No composer.lock file present. Updating dependencies to latest instead of installing from lock file. See https://getcomposer.org/install for more information.
Loading composer repositories with package information
Updating dependencies
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Root composer.json requires linked library lib-gmp >=6.5.0 but it has the wrong version installed or is missing from your system, make sure to load the extension providing it.

[Sebastix]

phpunit tests are failing (https://github.com/nostrver-se/nostr-php/actions/runs/11969646535) and when I searched why, this was the first result: php/php-src#16870

Is this issue also related to this PR?

[Sebastix]

I will also revert the commit in the main branch and will open an issue to follow the progress / updates on this.

When I test it with PHP version 8.2.26 this error occurs (using docker image php:8.2.6-alpine)
ValueError: base and exponent overflow in /nostr-php/vendor/uma/phpecc/src/Math/GmpMath.php on line 80 and it's related to php/php-src#16870

When I test it with PHP version 8.2.25 these errors don't occur (using docker image php:8.2.5-alpine).

@1ma See phpipam/phpipam@2414f86 for a possible temporary workaround which can be applied in the phpecc package.