qt: remove `MainTableView.qml`, and `MainGridView.qml`

0f616a46 made MainGridView.qml obsolete by introducing ExpandGridItemView.qml. ExpandGridItemView is supposed to be a generic view solely based on its name. However, ExpandGridItemView can not really be a generic view because it has displayMarginEnd: g_mainDisplay.displayMargin. This is problematic, and we are already suffering from this in the home page and the browse page where it is used as a sub-view, where we do not want to have extra display margins (as these pages have a parent flickable encapsulating the child views).

One might ask, why not introduce MainExpandGridItemView.qml? Because then all the pages that use it would then no longer be generic. Any component that uses a "Main" component becomes a "Main" component itself. If we really want that, we need to add Main suffix to all the pages. In fact, we already have this problem due to MainTableView, and I try to fix it here as well by making it obsolete (and removing it).

Although I don't like property forwarding, I think generic pages make more sense. If we want to continue having MainGridView and MainTableView, we need to add Main suffix to all the pages using these views (basically every page).

This also constitutes preliminary work for stopping accessing g_mainDisplay all over.

This is draft for now because it needs more testing.

Request review @chub.