Add MsBuild14 Integration Tests

[pavel-mikula-sonarsource]

Currently, we don't have a way how to test MsBuild14 support after MS deprecated VM images with it.

We need to

• Create a VM with MsBuild14 on it or reuse the one used in MsBuild14 peachee jobs.
• Use it in CI.
• Run some ITs on it, at least for basic scenarios.

[pavel-mikula-sonarsource]

We have a heads-up from RE that CI might need some changes.

So for now, it doesn't make sense to invest in changing CI to run on VM with MsBuild 14.

[costin-zaharia-sonarsource]

I'm closing this since soon we will no longer support MsBuild 14.