Improve Log handling in the easy-installer beyond being able to copy/paste it

Summary

At the moment it's not easily possible to share the log of the easy-installer.

Expand the "> Log" while using the installer, try to share the text.

It is not possible to copy/paste the text (I'd call that a bug, see #2096 (closed)) nor export it otherwise (my focus in this issue).

To make sharing logs more easy I could imagine three options

add a "save" button so that the complete log can be saved as a text file
add an "upload" buttons to automatically send the log to some pastebin-like service (the UBports Installer does it that way IIRC)
add a "submit problem report" button to automatically create an issue in gitlab with the log attached

What does it bring?

When people are stuck using the installer, having the full log in a ready-to-share way as easily as possible should speed up the support process.

Not sure if the log has to be scanned for sensitive information (serial numbers/IMEI etc.) before saving/uploading.