Clone wwwroot51 repositories wih proper credentials

Summary:
To clone repositories through SSH, and to clone private repositories,
SSH public/private keys pairs are stored in Vault.

DevCentral repositories use a key for alken-orin account.
BitBucket and GitHub repositories have their own deployment key.

The git.latest module method can then use the relevant key.

Fixes T1559.

Test Plan: Deploy on WindRiver

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1559

Differential Revision: https://devcentral.nasqueron.org/D3094