[FIR] Allow "missing from dependencies" severity names in opt-in usage checker

- KT-62397 occurs in the IDE because enum entry symbols from libraries
  are deserialized from stubs, which currently produce
  `FirFromMissingDependenciesNamedReference`.
- During opt-in usage checks, the compiler only considered resolved
  references when getting the severity name, but we can just take the
  name from the `FirFromMissingDependenciesNamedReference`.

^KT-62397 fixed

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirOptInUsageBaseChecker.kt

@@ -21,7 +21,8 @@ import org.jetbrains.kotlin.fir.declarations.utils.isData
 import org.jetbrains.kotlin.fir.declarations.utils.nameOrSpecialName
 import org.jetbrains.kotlin.fir.expressions.FirConstExpression
 import org.jetbrains.kotlin.fir.expressions.FirQualifiedAccessExpression
-import org.jetbrains.kotlin.fir.references.resolved
+import org.jetbrains.kotlin.fir.references.FirErrorNamedReference
+import org.jetbrains.kotlin.fir.references.FirNamedReference
 import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
 import org.jetbrains.kotlin.fir.resolve.toFirRegularClassSymbol
 import org.jetbrains.kotlin.fir.resolve.toSymbol
@@ -273,7 +274,13 @@ object FirOptInUsageBaseChecker {
             ?: return null
 
         val levelArgument = experimental.findArgumentByName(LEVEL) as? FirQualifiedAccessExpression
-        val levelName = levelArgument?.calleeReference?.resolved?.name?.asString()
+
+        val levelName = when (val calleeReference = levelArgument?.calleeReference) {
+            is FirErrorNamedReference -> null
+            is FirNamedReference -> calleeReference.name.asString()
+            else -> null
+        }
+
         val severity = Experimentality.Severity.values().firstOrNull { it.name == levelName } ?: Experimentality.DEFAULT_SEVERITY
         val message = (experimental.findArgumentByName(MESSAGE) as? FirConstExpression<*>)?.value as? String
         return Experimentality(symbol.classId, severity, message, annotatedOwnerClassName)