feat(payments-next): Add free trial configuration to Strapi

Because:

* Relying Parties should be able to control the details of a free trial including marketing language specific to the free trial.

This commit:

* Adds free trial query, util, factories, types to fetch free trials records.
* Updates ProductConfigurationManager to return the content

Closes #[PAY-3542](https://mozilla-hub.atlassian.net/browse/PAY-3542)

Author: elizabeth-ilina