FIR LL: fix searching logic for enum entry

KtEnumEntry, a subtype of KtClass, has been handled by
findNonLocalClass. Since KtEnumEntry doesn't have class id, that util
always throws an error while retrieving class id.

Instead, we should use containing class (i.e., enum class) id.
Also, once the enum class is resolved, we should search for matching
enum entry inside the enum class.

analysis/low-level-api-fir/testdata/getOrBuildFir/annotations/retentionValue.kt

@@ -0,0 +1,2 @@
+@Retention(AnnotationRetention.<expr>SOURCE</expr>)
+annotation class Anno

analysis/low-level-api-fir/testdata/getOrBuildFir/annotations/retentionValue.txt

@@ -0,0 +1,5 @@
+KT element: KtNameReferenceExpression
+FIR element: FirResolvedNamedReferenceImpl
+
+FIR element rendered:
+R|kotlin/annotation/AnnotationRetention.SOURCE|