envvars-dialog: Center text entry vertically

Traverse AdwEntryRow's widget tree to remove visibility of the title labels and change alignment of the text entry to center.

This implementation is tightly coupled with the internal representation of AdwEntryRow. Checks were added to prevent crashing if that representation changes, but in such case the layout may get askew.

bottles/frontend/windows/envvars.py

@@ -17,9 +17,12 @@
 
 from gi.repository import Gtk, GLib, Adw
 
+from bottles.backend.logger import Logger
 from bottles.frontend.utils.gtk import GtkUtils
 from bottles.frontend.utils.sh import ShUtils
 
+logging = Logger()
+
 
 @Gtk.Template(resource_path="/com/usebottles/bottles/env-var-entry.ui")
 class EnvVarEntry(Adw.EntryRow):
@@ -44,6 +47,21 @@ def __init__(self, parent, env, **kwargs):
         self.connect("apply", self.__save)
         self.btn_remove.connect("clicked", self.__remove)
 
+        try:
+            widget = self.get_child().get_first_child().get_next_sibling().get_first_child()
+            while isinstance(widget, Gtk.Label):
+                widget.set_visible(False)
+                widget = widget.get_next_sibling()
+
+            if isinstance(widget, Gtk.Text):
+                widget.set_valign(Gtk.Align.CENTER)
+            else:
+                raise RuntimeError("Could not find widget Gtk.Text")
+        except Exception as e:
+            logging.error(
+                f"{type(e)}: {e}\nEnvVarEntry could not find text widget. Did AdwEntryRow change it's widget tree?"
+            )
+
     def __save(self, *_args):
         """
         Change the env var value according to the