Allow selecting for copy to clipboard only part of message text

### Your use case

#### What would you like to do?
Add ability to select and copy to clipboard only a part of full message text.

#### Why would you like to do it?
Very often I need to copy from a message text only part of the whole text, common ones are phone numbers, addresses, names, etc.

But Element-Android allows me to copy only the whole message text.

#### How would you like to achieve it?
On Long-Click menu we can add an item "Copy text selective" that will open a modal window with message text, where we can manually select desired fragment and copy it to clipboard.

This way is implemented in great app for VK.com social network [Kate Mobile](https://play.google.com/store/apps/details?id=com.perm.kate_new_6) and it's very useful and convenient!

### Have you considered any alternatives?

Alternative can be allow selecting of text parts inside timeline, but this will make behavior more complex, together with swiping and long-click menus.

### Additional context

_No response_