BTagging config flags creation

Create first version of BTaggingConfigFlags.py to be used in new configuration files.

A patch proposed in !25465 (merged) is implemented. @wlampl added for comments. It solved two issues for my BTagRun3Config.py script:

• with 2 threads, OutputStreamESD was frequently in ERROR state
• when the job were successful some variables were missing in the output

Control/AthenaConfiguration/python/AllConfigFlags.py

@@ -173,6 +173,11 @@ def _createCfgFlags():
         return createPFConfigFlags()
     _addFlagsCategory(acf,"PF",__pflow, 'eflowRec')
 
+    def __btagging():
+        from BTagging.BTaggingConfigFlags import createBTaggingConfigFlags
+        return createBTaggingConfigFlags()
+    _addFlagsCategory(acf,"BTagging",__btagging, 'BTagging')
+
     def __dq():
         from AthenaMonitoring.DQConfigFlags import createDQConfigFlags, createComplexDQConfigFlags
         dqf = createDQConfigFlags()