feat: improve multiple deletion process

[Wizzzzzzard]

Summary:
Implements a single confirmation dialog for multi-file deletion instead of prompting for each file individually. When users select multiple files or folders and choose to delete them via the context menu, they now see one confirmation dialog showing the total count of items to be deleted, rather than being prompted separately for each item.

• Added new localized messages (DeleteMultipleWarningMessage, RecycleMultipleWarningMessage, RecycleMultipleDirtyWarning) in const.ts to support batch deletion confirmations
• Refactored the deleteResource command in index.ts to collect all selected items and show a single confirmation based on the total count

Addresses #1290

Testing:
How did you test this change?

1. Sign in with a valid Viya connection
2. Open SAS Server or SAS Content in the explorer
3. Select multiple files and/or folders (use Cmd/Ctrl+Click or Shift+Click)
4. Right-click and select "Delete" from the context menu
5. Verify that only ONE confirmation dialog appears showing the count of items (e.g., "Are you sure you want to permanently delete 5 items?" or "Are you sure you want to move 3 items to the Recycle Bin?")
6. Test with a single file selection to ensure the original behavior is preserved (shows file name in confirmation)
7. Test with folders containing unsaved files to verify the appropriate warning message appears

TODOs:

• Add any supporting documentation and (optionally) update CHANGELOG.md

[Wizzzzzzard]

To test I created a folder and several files under tmp then selected them all and hit delete. That produces this dialogue:

Selecting delete confirmed to remove the files!

[Wizzzzzzard]

Also still works when deleting a single item:

Prompts again if trying to delete a file with unsaved changes:

[Wizzzzzzard]

Deleting more than 10 files truncates the list as well:

[allenfrazelle-vsce]

Looks good, thanks Elijah!

[scottdover]

Hey @Wizzzzzzard. I haven't looked through all of this yet, but here are my general thoughts:

• It was decided a while ago that we don't need a confirmation when moving files to a recycle bin. My assumption is that that still holds. With that in mind, I think we can remove the recycling bin notifications
• For deletion, since the number of deletions is somewhat unbounded, I'd suggest keeping it simple and having two messages: One for single deletion, and one for multiple deletion. For multiple deletion, I'd stick to a message like "Are you sure you want to permanently delete {count} items?" without relying on spelling out every file. That'll hopefully cut down on some of the logic here
• Last, for the dirty files issue, I'm wondering if a single message like this works for all cases: "The selected folders contain unsaved files, are you sure you want to delete?"

[Wizzzzzzard]

@scottdover I've actioned your feedback by removing the recycling notifications and simplifying the delete logic down, if you would be ok to re-review when you get the chance? :)