Enhancing work with attachments

### Your use case

Hello. The desktop version of Element has a few problems with attachments that make me very sad.

1. When we try to download an attachment from a chat room, it is downloaded first, and only then is the choice of the directory to save the file requested. This looks ugly when the files are large, because you have to wait a long time (nothing happens on the client screen while waiting).
**Solution**: First select a storage location and only then download the attachment;

2. When downloading an attachment from chat, a temporary file is used, which is saved to the system hard drive. This behavior is incorrect because there may not be enough space on the system drive for an attachment of large size. Moreover, why do we need it at all? It looks like an overhead.
**Solution**: We should at least first ask the user for storage space for the attachment (which will probably not be on the system disk);

3. There is no progress bar to track the process of downloading an attachment.
**Solution**: add a progress bar to improve user experience;

4. There is no option to define a default location for downloading attachments in the settings, so that we don't have to choose it every time.
**Solution**: add this feature (optional);

5. The same attachment is downloaded every time, this is extremely inconvenient and not optimal (imagine that the attachment weighs 100+ mb).
**Solution**: We should download the attachment once and remember it. Given that attachments can be saved in different places, we should consider logging where and which attachments are saved;

6. It is possible to upload an attachment via drag-and-drop to chat. But there is no such option to copy via drag-and-drop an already downloaded attachment from chat (in fact, the copying will happen locally). This is a very useful feature when you need to quickly copy an attachment to another location. Note that this task depends on (5).
**Solution**: add this feature;

7. When we right-click on an attachment there is no way to open the directory in which the attachment is saved.
**Solution**: add this feature. Note that this task depends on (5).

### Additional context

I expect that many users of the wonderful Element will be so happy if these features are implemented, especially (5).