Usage of accessing a namespace at runtime via "mx_internal::" should be changed to "use namespace mx_internal"

There are roughly 800 places we use "mx_internal::" in our code. If we can't optimize this at the compiler level, then we should switch most (or all) to the "use namespace mx_internal" syntax. This should yield better compiler and runtime performance. Ideally, we could get ASC to change this for us, though.