Purpose:

The disaggregated fast truncate feature (POC) is merged into develop behind the WT_DISAGG_FAST_TRUNCATE_BUILD cmake flag, which defaults to OFF. This means the develop waterfall has no visibility into whether fast truncate works via testing.

A dedicated Evergreen project is needed to run the existing test suite with the flag enabled to provide a continuous signal on the feature's health. This needs to be done without enabling it by default on develop until the feature is ready.

Definition of Done:

1. test/evergreen.yml configure function supports injecting the -DWT_DISAGG_FAST_TRUNCATE_BUILD flag.
2. An Evergreen project is set up to enable the flag at the project level.