Show input fields for all tags at once in the tag create/edit dialog

[pascalwittler]

Current behavior

• If you want to add a tag, you have to select its key from a drop-down menu and then enter its value in the single text input next to it before hitting the "Add" button.
• After adding a tag, the drop-down menu on the left always returns to the first existing option which means that if you do not want to enter a value for the first tag(s) but for a set of tags lower in the list, you have to open the drop-down menu each single time to select a different tag.
• If you edit a tag value later, leaving the input field automatically saves the new value which is nice but inconsistent with the workflow for adding new tags above (where you have to click "Add") and you get no visual feedback to make sure the value was successfully saved to the database.
• The order of the input fields (as well as the order of the tag list below your status) is different for each status, depending on the order you selected and filled them (see also Sort Tags #2230)

Desired behavior

I would like to see all text input fields for each existing tag key at once, so you can add or edit as many values as you want and just leave the other text fields empty. After leaving an input field, some visual feedback to indicate the successful saving would be great. The order can always be the same and you can enter or change values in any order you like without having to use the mouse or opening/closing a drop-down menu each time. Pressing the [TAB] key on devices with hardware keyboards would also work.