fix: MapComparator overflow causes SQL stat sort to fail

[daguimu]

Problem

SQL monitoring page sort doesn't work — clicking column headers toggles the ▲▼ icons but the data order doesn't change. Descending sort has no effect.

Root cause: MapComparator uses (int)(longA - longB) for Long/Date/Number comparisons. When values are large (which is common for cumulative SQL stats like ExecuteCount and TotalTime), the subtraction overflows int range, producing wrong comparison results that violate the Comparator contract.

Example: (int)(3000000000L - 1L) = -1294967297 (negative! should be positive)

This causes Collections.sort to produce unpredictable ordering that doesn't change between ascending and descending mode — exactly matching the reported behavior.

Fix

Replace all 3 overflow-prone comparisons with safe alternatives:

Before (overflow)	After (safe)
(int)(long1 - long2)	Long.compare(long1, long2)
(int)(double1 - double2)	Double.compare(double1, double2)
(int)(date1.getTime() - date2.getTime())	Long.compare(date1.getTime(), date2.getTime())

The Double.compare fix also resolves a precision bug where small differences (e.g., 100.5 - 100.0 = 0.5) were truncated to 0 by the (int) cast, treating close values as equal.

Tests Added

7 new test cases in MapComparatorOverflowTest.java:

• test_long_sort_ascending_large_values — ASC sort with Long.MAX_VALUE range
• test_long_sort_descending_large_values — DESC sort with Long.MAX_VALUE range
• test_long_sort_desc_differs_from_asc — verifies DESC produces reverse of ASC
• test_long_overflow_values — specific overflow case: 3B vs 1
• test_date_sort_large_time_difference — Date comparison with epoch vs now
• test_number_small_difference_precision — 100.5 vs 100.0 precision
• test_random_long_sort_consistency — 100 random Longs, no TimSort contract violation

All 4 existing MapComparatorTest tests continue to pass.

Impact

Fixes SQL statement monitoring page sort for all stat columns (ExecuteCount, TotalTime, MaxTimespan, etc.). The fix is minimal (3 line changes) with no behavioral change for values within int range.

Fixes #6624