LocationBar: Use GtkStack to manage three independet widgets for search/path-entry/breadcrumbs
Original Title: It's possible to start searching by typing "Search: " in the Location bar, but search mode is not entered
Version: Thunar git main as of 909efefedbc28716863f754e00a804bc81c93975.
## Steps to reproduce
As the title says, it is possible to start a new search by pressing <kbd>Ctrl+L</kbd> (`Open Location…`) and entering a string such as "`Search: some search terms`". However the display isn't the usual search listing: if you are in Icon View to start with, the search results are shown in Icon Vew too:
<details><summary>Click to expand screenshot</summary>

</details>
This "search" cannot be terminated with <kbd>Esc</kbd>, and the search togglebutton on the toolbar is not toggled on.
### Continued weirdness
If you now press the more conventional <kbd>Ctrl+F</kbd> combination (`Search for Files…`), then a new "real" search begins. It's as if Thunar wasn't in search mode at all before, despite the search results clearly showing!
<details><summary>Click to expand screenshot</summary>

</details>
The results are shown in List View, which is what I expect, and now the Search button is toggled on. This search can be terminated with <kbd>Ctrl+F</kbd> or <kbd>Esc</kbd> while the search entry box has focus and Thunar will switch back to Normal mode.
## Observations
Thunar should enter "proper search mode" no matter which keys you press to initiate the search. This becomes important if one fix for #787 would be to stop monitoring while in search mode.
I don't like the search entry box being actually the location entry box with some editable text stuffed in the front somehow. It seems to lead to situations like this when you consider that strings have to be parsed. I think I'd prefer two separate boxes in a GtkStack whose state gets toggled when you press <kbd>Ctrl+F</kbd>, <kbd>Ctrl+L</kbd>, or <kbd>Esc</kbd>. If there's to be text at the front of the search entry box, make it static and uneditable so that I can press <kbd>Ctrl+A</kbd> to go to the start of the search string like a normal text entry box.
issue