Task cache pre-heat

[SimaTian]

Most of tasks MSBuild uses are not intrinsic - e.g. they need to be located and loaded into the assembly. This loading has a visible runtime impact:

This is happening first time any task is loaded to be executed - afterward it is cached.

We could pre-heat the cache as soon as we first encounter the task name (e.g. during XML parsing). This could allow for a neat parallelization use case that should be contained enough so as not to cause issues elsewhere.

[KalleOlaviNiemitalo]

I suppose pre-heating of task types should be disabled if the -getProperty or -getItem option is used and no targets are going to be executed.