fix(feed-sitemap): parse EXIF tag generation and streamline date handling

- Updated EXIF tag generation to utilize PickedExif type for better type safety.
- Simplified date handling in generateExifTags function to improve readability.
- Removed redundant code and improved the handling of various EXIF properties.
- Enhanced GPS coordinate normalization and added utility functions for better clarity.

Signed-off-by: Innei <tukon479@gmail.com>

Author: Innei