fix: add copy, rename, and delete as unsaved actions properly

[jotalis]

Summary

• Copying, renaming, and deleting schedules are now stored as unsaved actions and can be re-loaded if the user wants to
• Fixes "an issue where duplicating a schedule that was not currently selected would incorrectly create a new schedule containing the events of the currently selected schedule, instead of duplicating the intended schedule," a bug also fixed in feature/drag-and-drop schedules #1089; will fix merge conflicts after either one gets merged into main
• Slight code refactoring for consistency

Test Plan

• Create several schedules with some events. Duplicate, rename, and delete some. Take note of the order and state of these schedules. Reload the page without saving these changes and load the unsaved changes. Ensure the loaded changes match the schedule states prior to reloading

Closes #1090

[KevinWu098]

LGTM, great feature improvement, however there's still a bit of bugginess as newly created schedules aren't logged in the action states, and thus actions upon newly created schedules then don't get applied

[KevinWu098]

LGTM, just the one comment above

[KevinWu098]

LGTM 🚀