Compared to FE1.0, instead of using UNRESOLVED_REFERENCE, a new
UNRESOLVED_IMPORT diagnostic is introduced. This is so that we can use a
different positioning strategy to highlight the last part of the import
if the entire import is passed.
Also, this change fixed some incorrectly rejected imports in FIR. Such
cases are covered the newly added test file staticFunAndPropertyImport.kt
Tianyu Geng
18f7a760bb