Add factory to generate TriggerBuild classes

Summary:
A factory class allow to prepare a service provider
to get TriggerBuild instances, configuring only once
a HTTP client and the tokens to use.

Ref T959.

Test Plan:

• new tests
• test implementation for Notifications center, as a Laravel service provider.

Reviewers: dereckson

Maniphest Tasks: T959

Differential Revision: https://devcentral.nasqueron.org/D650