hgview #87901 simplify toolbar [validation pending]

move actions from toolbar to content menu.

prioritynormal
typeenhancement
done in1.6.0
load2.000
load left0.000
closed by#133acb2b057d [curses] disable lazy import (from Hg) for urwid (closes #87901), #0f6fcebcd9cb [qt] move diff actions from toolbar to context menu and hide toolbar diff at startup (closes #87901)