Add new `SnoozeMany` and `UnsnoozeMany` mutations for todos

What does this MR do and why?

Add two new mutations for todos: SnoozeMany and UnsnoozeMany. We need these for the upcoming Bulk edit to-dos (#16564 - closed) feature.

References

• Part of Bulk edit to-dos (#16564 - closed)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

recording_1738340602

How to set up and validate locally

• Test the new mutations in the http://gdk.test:3000/-/graphql-explorer
• Also verify that the existing migrations ResolveMany and RestoreMany still work as before. Those use the same abstract base class which saw a little change in this MR.