Since getting results from mainline builds is usually doesn't have someone waiting for it like patch builds do, we may want to make different tradeoffs when splitting tasks in the maintain vs splitting tasks in patch builds. We are already treating dependencies differently for splitting tasks in patch builds vs mainline builds. So also applying that to the number of tasks split should be fairly straight-forward.

As an evergreen server maintainer,
I want to be able to specify different task splitting configurations for mainline vs patch builds,
So that I can customize how tasks are split based on the situation.

AC:

• mainline builds and patch builds can have different targets for number of tasks to split.
• mainline builds cap the numbers of subtasks to 1.