[release/6.0] Fix Crossgen2 bug #61104 and add regression test (#64027)

[release/6.0] Fix Crossgen2 bug #61104 and add regression test (#64027)

* Fix issue #61104 and add regression test

The issue tracks the runtime regression failure where
Crossgen2-compiled app is unable to locate a type with non-ASCII
characters in its name. The failure was caused by the fact that
Crossgen2 was incorrectly zero-extended the individual characters
when calculating the hash whereas runtime is sign-extending them.

Thanks

Tomas

* Simplify the regression test per Anton's PR feedback

Co-authored-by: Tomas <trylek@microsoft.com>