fix: add validation for names of task queue funcs

[IzaakGough]

Fixes #7365

This PR adds validation for task queue function names, ensuring that, in particular, they don't include underscores.

Testing

• Manually verified that attempting to deploy a task queue function with a name containing an underscore is met with an informative error.
• Automated tests pass

[gemini-code-assist]

Code Review

This pull request introduces validation for task queue function names at deploy time to ensure they conform to Cloud Tasks queue ID naming rules, which prohibit underscores and limit names to 100 characters. It adds the taskQueueFunctionNamesAreValid validation function, integrates it into the deployment pipeline, and includes corresponding unit tests and a changelog entry. There are no review comments, and I have no additional feedback to provide.