XUnitLogChecker: Consolidate duplicated properties in coreclr and libraries into one place #94802

There are various property values that could be placed in a central location and only defined once. For example:

A) This property that determines if XUnitLogChecker is supported, is already in a central location:

It is a very similar condition to the one used in the coreclr specific code:

B) The coreclr paths:

Could also be merged into the same paths used by libraries:

C) The build task in Libraries does this:

and the collection of the built artifacts is done here:

While coreclr restores/builds it in this file:

So there's also an opportunity to merge these two into a single centralized one.