Move `wp-pay-gateways/*` and `wp-pay-extensions/*` to `pronamic/wp-pronamic-pay-*`

[remcotolsma]

Useful for organization-wide projects: https://github.com/orgs/pronamic/projects?type=beta.

• https://github.com/wp-pay-gateways/
• https://github.com/wp-pay-extensions/

[remcotolsma]

For 8.1 I think it's good to address this issue, I propose the following naming:

• https://github.com/wp-pay-gateways/mollie → https://github.com/pronamic/wp-pronamic-pay-mollie
• https://github.com/wp-pay-extensions/woocommerce → https://github.com/pronamic/wp-pronamic-pay-woocommerce

There is not a very clear distinction between gateway and plugin integrations anymore, but we can use repository labels for that.

We can work towards each integration becoming a plugin/addon:

• Pronamic Pay Adyen Add-On
• Pronamic Pay Mollie Add-On
• Pronamic Pay WooCommerce Add-On

If there are no objections or additions, I will start the migration next week.

[remcotolsma]

Moved:

• https://github.com/topics/wp-pronamic-pay-extension
• https://github.com/topics/wp-pronamic-pay-gateway