[Enhancement] Allow labels to be retained when mail is transferred to `/trash`.

Prerequisites

1. I have searched open and closed issues for duplicates

2. This isn't a feature request

3. This is not a report about my app not working as expected

Problem And Solution

When protonmail.uservoice.com/forums/284483-proton-mail/suggestions/13005873-trash-and-labeled-emails was "COMPLETED", ^1 no option was introduced to disable the new functionality. This means that I am unable to utilise /trash without losing labels. An easy solution is to create a new folder. However, habit makes ensuring that I utilise the new folder difficult without a way to disable /trash. Consequently, allow the user to disable the automatic tag removal upon deletion.

Tasks

1. File this as a suggestion at protonmail.uservoice.com/#suggestion_title.

2. Wait for protonmail.uservoice.com/forums/945460-general-ideas/suggestions/50436528 to be implemented, so that this can be filed as a bug via the correct avenue.

No source files or tests are named. Start by reviewing the linked UserVoice entry and the referenced bug-tracker suggestion to establish the intended product path. The issue's stated completion is filing the suggestion through the correct avenue, or waiting for the referenced bug-tracker change.