Change weight priority type from Integer to Float

[molcay]

This PR is about changing the type of priority_weight property of the TaskInstance. For different databases, we have different possible max values for the integer columns.

There are several attempts to fix this problem:

• Prevent breaking scheduler on task_instance.priority_weight column has overflow value apache/airflow#22784
• Validate DAG task_instance.priority_weight column overflow value during import apache/airflow#34168
• Validate tasks total priority weight in DagBag apache/airflow#37990
• Hard limit priority weight total by int32 value apache/airflow#38125
• Change weight priority type from Integer to Float apache/airflow#38160

This PR contains the changes in apache#38160 (created by Taragolis) on top of apache#38222 as mentioned here.

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