Rework the MAP metric. (#8931)

- The new implementation is more strict as only binary labels are accepted. The previous implementation converts values greater than 1 to 1.
- Deterministic GPU. (no atomic add).
- Fix top-k handling.
- Precise definition of MAP. (There are other variants on how to handle top-k).
- Refactor GPU ranking tests.

tests/cpp/common/test_ranking_utils.h

@@ -6,4 +6,6 @@
 
 namespace xgboost::ltr {
 void TestNDCGCache(Context const* ctx);
+
+void TestMAPCache(Context const* ctx);
 }  // namespace xgboost::ltr