feat: add sigterm handler to gracefully shutdown worker and log

[YunchuWang]

Description

this adds the sigterm handler to gracefully shutdown the python worker and exit with successful code(0). Context can be traced in https://teams.microsoft.com/l/message/19:b0220a1e0c884a66a7f133247573434b@thread.tacv2/1726245777081?tenantId=72f988bf-86f1-41af-91ab-2d7cd011db47&groupId=201c2bb2-812d-4986-ac92-9bfad0d6cc59&parentMessageId=1726245777081&teamName=Azure%20Functions%20Team&channelName=Servicing%20-%20Sev2s%2C%20CRIs%20and%20general%20guidance&createdTime=1726245777081

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