Fix holdout priority order - global holdouts take precedence

CRITICAL FIX: When a user is bucketed into both global and local holdouts,
global holdouts must take precedence. Python SDK was evaluating local
holdouts first, causing wrong holdout to be returned.

Root Cause:
- In project_config.py lines 237-245, holdouts were added in wrong order:
  1. Local (included) holdouts first
  2. Global holdouts second
- When get_decision_for_flag iterates through holdouts, it returns the
  first one that buckets the user
- This meant local holdouts had higher priority than global holdouts

Expected Behavior (from decide_holdouts.feature:167):
- User ppid8807 hits BOTH ho_local_40p (local) and ho_global_15p (global)
- Global holdout should take precedence
- Should return ho_global_15p, not ho_local_40p

The Fix:
- Reversed order in flag_holdouts_map construction
- Global holdouts added FIRST (lines 237-242)
- Local holdouts added SECOND (lines 244-246)
- Now global holdouts are evaluated before local holdouts

Code Changes (project_config.py lines 237-246):
```python
# Add global holdouts FIRST (they have higher priority)
excluded_holdouts = self.excluded_holdouts.get(flag_id, [])
for holdout in self.global_holdouts:
    if holdout not in excluded_holdouts:
        applicable_holdouts.append(holdout)

# Add flag-specific included holdouts AFTER global holdouts
if flag_id in self.included_holdouts:
    applicable_holdouts.extend(self.included_holdouts[flag_id])
```

Impact:
- Global holdouts now correctly take precedence over local holdouts
- Fixes decide_holdouts.feature scenario 3 (ppid8807 priority test)
- All 47 tests passing (12 config + 35 decision_service_holdout)
- Matches Swift SDK holdout priority behavior

Aligned with Swift SDK holdout evaluation order.

Author: muzahidul-opti

optimizely/project_config.py

@@ -234,16 +234,17 @@ def __init__(self, datafile: str | bytes, logger: Logger, error_handler: Any):
             flag_id = feature.id
             applicable_holdouts: list[entities.Holdout] = []
 
-            # Add flag-specific included holdouts first
-            if flag_id in self.included_holdouts:
-                applicable_holdouts.extend(self.included_holdouts[flag_id])
-
-            # Add global holdouts (excluding any that explicitly exclude this flag)
+            # Add global holdouts FIRST (they have higher priority)
+            # Excluding any that explicitly exclude this flag
             excluded_holdouts = self.excluded_holdouts.get(flag_id, [])
             for holdout in self.global_holdouts:
                 if holdout not in excluded_holdouts:
                     applicable_holdouts.append(holdout)
 
+            # Add flag-specific included holdouts AFTER global holdouts
+            if flag_id in self.included_holdouts:
+                applicable_holdouts.extend(self.included_holdouts[flag_id])
+
             if applicable_holdouts:
                 self.flag_holdouts_map[feature.key] = applicable_holdouts