Symbolsolver import order #2521
This PR solves two problems.
A single-type-import (JLS 7.5.1) and a single-static-import(JLS 7.5.3) can import same name into a compilation unit, when the static-imported name doesn't refer a type (e.g., enum member, etc.).
Thanks @MysterAitch for your review.
As you commented, the assertion messages were not descriptive enough for the test cases.
If you could tell me your preference for this project, I will follow the guideline.