[ENHANCEMENT] Limit number of automatically exported timestamped "installed packages" JSON backups to X

### Please confirm these before moving forward

- [X] I have searched for my feature proposal and not found a work-in-progress/duplicate/resolved/discarded issue.
- [X] This improvements refers to an existing feature. If you want to suggest a new feature, please use [this template](https://github.com/marticliment/WingetUI/issues/new?assignees=marticliment&labels=new-feature&projects=&template=feature-request.yml&title=%5BFEATURE+REQUEST%5D+%28Enter+your+description+here%29)
- [X] This improvements is not a bug. If you want to report a bug, please use [this template](https://github.com/marticliment/WingetUI/issues/new?assignees=marticliment&labels=bug&projects=&template=bug-issue.yml&title=%5BBUG%5D+%28Enter+your+description+here%29)

### Describe the improvement

The settings gives us options to automatically export a list of all packages after login. When the option to include timestamps is enabled, it appears that there is no limit to how many "installed packages" JSONs are created. A UI element to set the max number of backups would be appreciated.

### Describe how this improvement could help users.

A limit on the number of timestamped "installed packages" JSONs would help by keeping the size of the exported-to directory under control (it could balloon in size after many months of exports). Some users may prefer this remaining unlimited, but I would personally prefer to limit this to 30 backups (FIFO).