Feature request: Add option to remove the “Close tab” button

### Is your feature request related to a problem?

There are alternatives such as extensions which add “Close tab” button into toolbar. In example this: https://addons.mozilla.org/en-US/firefox/addon/close-the-tab-button/

### The solution I'd like

Add a `about:config` option to remove the “Close tab” button from tabs, with these options: “Remove only from inactive tabs”, “Remove from all tabs”, and option “Hover on inactive tabs”.

### Screenshots or video

_No response_

### Alternatives I've considered

_No response_

### Additional context

_No response_

Start by reviewing the repository’s existing Firefox tab styling and about:config options, then identify where the Close tab button is controlled. Implement the requested modes for inactive tabs, all tabs, and hover behavior, and verify each mode in Firefox.

Written by the indexing model from the issue text.