MissingDependencyClassChecker.collectDiagnostics now show only unique diagnostics
As per-file analyzer trace used in checker delegates to resolve session trace, diagnostics might be duplicated because of race condition:
1. If a non-checker thread performs analyze first, diagnostics for global elements will be stored in the resolve session trace only once.
2 If the checker threads comes to the analyze first, diagnostics will be stored in the local trace, and after that might be duplicated in the resolve session trace by other analyzers.
#KT-35578 Fixed
Nikolay Krasko
e99dc0f87f