[ios] Import kml, kmz, gpx files using the default document picker

[kirylkaveryn]

Closes #7866 (comment)

This PR implements the kml, kmz, gpx files importing in iOS using the default UIDocumentPickerViewController.

nits:

1. The icon was designed by me and requires an update @euf can you please help?
2. The alerts are stacked one by one so it needs to be updated to handle multiple files importing at once.

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Results:

ios 17.2

ios12.5

RPReplay_Final1717775598.MP4

[euf]

Hello, I'll provide new icons asap 👀

[euf]

Please try these icons for both import and export (updated):

If you could share a screenshot with them, I'd be very grateful!

[kirylkaveryn]

Please try these icons for both import and export (updated):

If you could share a screenshot with them, I'd be very grateful!

@euf
Thanks a lot!
Here is the result:

[kirylkaveryn]

The file import is limited by one.
The multiple files import should be implemented as part on another PR.

[biodranik]

LGTM, it would be great to also support import of kmb files.

[rtsisyk]

Please add support for multiple files, like on Android. This is the entire purpose of this feature. One file can be imported via sharing from Files app. Please don't overthink this batch import. Android has worked for 3+ years and nobody ever worried about multiple alerts shown and possible of partial import.

[biodranik]

The main purpose of this PR is to make import discoverable for users. It is at the top of UX issues right now, many users do not understand that GPX/KML/KMZ files can be imported.

The first step is to solve the main issue and allow single file import, without breaking existing code/without risks of introducing bugs.

The next step is to introduce multiple file selection and to carefully test it everywhere, including Android.