Combine the Text style and Apply last toolbar button

[Daniel]

I have seen that there is a new functionality of the Apply last button 
to choose from the Text style history via a drop down menu 
(https://wiki.lyx.org/LyX/NewInLyX24#ui). Seems to me that this is a 
good opportunity to get rid of the Apply last toolbar button altogether. 
Just add the drop down menu to the Text style button. The catch is of 
course that applying the last used style takes one click more. But maybe 
there could be a keyboard shortcut to do this task even quicker for 
those who need it? The keyboard shortcut could be shown together with an 
Apply last entry in the Edit > Text style menu or the first entry of the 
Text style history.

I think getting rid of the button in this way is good because

1. it better groups the Text style features
2. it saves space for other toolbar buttons to be shown

Daniel