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:[email protected]/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

---

PR information

• The title of the PR is clear and informative.
• There are a small number of commits, each of which has an informative message. This means that previously merged commits do not appear in the history of the PR. For information on cleaning up the commits in your pull request, see this page.
• If applicable, the PR references the bug/issue that it fixes in the description.
• New Unit tests were added for the changes made and CI is passing.

Quality of Code and Contribution Guidelines

• I have read the contribution guidelines.