Kotlin: keep full value class coverage focused

Replace the secondary constructor's Long conversion with a String overload.
This preserves coverage for non-trivial value-class construction without
exercising an unrelated primitive-conversion diagnostic.

This is a test-only refinement and does not change extractor behaviour.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: andersfugmann

java/ql/test-kotlin2/library-tests/full-value-classes/test.expected

@@ -10,8 +10,8 @@ properties
 constructors
 | test.kt:3:1:5:1 | Base | Base() |
 | test.kt:7:22:7:65 | PairValue | PairValue(int,java.lang.String) |
-| test.kt:8:5:8:68 | PairValue | PairValue(long) |
+| test.kt:8:5:8:58 | PairValue | PairValue(java.lang.String) |
 constructorCalls
 | test.kt:7:1:9:1 | super(...) | test.kt:3:1:5:1 | Base |
-| test.kt:8:32:8:68 | this(...) | test.kt:7:22:7:65 | PairValue |
-| test.kt:11:40:11:55 | new PairValue(...) | test.kt:8:5:8:68 | PairValue |
+| test.kt:8:34:8:58 | this(...) | test.kt:7:22:7:65 | PairValue |
+| test.kt:11:42:11:57 | new PairValue(...) | test.kt:8:5:8:58 | PairValue |

java/ql/test-kotlin2/library-tests/full-value-classes/test.kt

@@ -5,7 +5,7 @@ abstract value class Base {
 }
 
 value class PairValue(override val value: Int, val label: String) : Base() {
-    constructor(value: Long) : this(value.toInt(), value.toString())
+    constructor(value: String) : this(value.length, value)
 }
 
-fun makePairValue(value: Long): Base = PairValue(value)
+fun makePairValue(value: String): Base = PairValue(value)