FIR: fix memory leak from ConeIntegerLiteralTypeImpl via static NUMBER_TYPE

ConeClassLikeType has a cachedExpanded type which has a strong ref to FirSession

compiler/fir/tree/src/org/jetbrains/kotlin/fir/types/ConeIntegerLiteralTypeImpl.kt

@@ -62,7 +62,7 @@ class ConeIntegerLiteralTypeImpl : ConeIntegerLiteralType {
 
     override val supertypes: List<ConeClassLikeType> by lazy {
         listOf(
-            NUMBER_TYPE,
+            createType(StandardClassIds.Number),
             ConeClassLikeTypeImpl(COMPARABLE_TAG, arrayOf(ConeKotlinTypeProjectionIn(this)), false)
         )
     }
@@ -83,8 +83,6 @@ class ConeIntegerLiteralTypeImpl : ConeIntegerLiteralType {
             return ConeClassLikeTypeImpl(ConeClassLikeLookupTagImpl(classId), emptyArray(), false)
         }
 
-        private val NUMBER_TYPE = createType(StandardClassIds.Number)
-
         private val INT_RANGE = Int.MIN_VALUE.toLong()..Int.MAX_VALUE.toLong()
         private val BYTE_RANGE = Byte.MIN_VALUE.toLong()..Byte.MAX_VALUE.toLong()
         private val SHORT_RANGE = Short.MIN_VALUE.toLong()..Short.MAX_VALUE.toLong()