API Use class from new template engine module

[GuySartorelli]

The template engine code is in its own module now, so we need to add it as a dependency and update the use statement. Going with API since that feels like it takes precedence over DEP and updating a use statement feels like a API commit to me, but I'm happy to change the prefix if the reviewer wants me to.

CI for this can't go green until silverstripe/silverstripe-framework#11451 has been merged

Issue

• Abstract template layer into its own dedicated module silverstripe-framework#11322