Codechange: Make all NWidgetPart arrays constexpr.

This ensures that the arrays are not created at runtime and prevents using non-constexpr values.

Codechange: Replace mishmash of types for widget index with WidgetID.

Indices were stored as int, but often passed around as uint/uint8_t and casts.

Now they should all use WidgetID.

Change: Hide bevel for resizeable sparse layout windows. (#11572)

When clicked, the button is still highlighted to show that it is active.

The bevel is controlled with widget_data by RWV_SHOW_BEVEL or RWV_HIDE_BEVEL values.

Codechange: Remove FONT_HEIGHT_... macros. (#11481)

These make it look like we're dealing with a constant, but actually each is a call to `GetCharacterHeight(...)`.

Codechange: Add __FILE__/__LINE__ of WindowDesc to WindowDesc.

This is to allow unit-tests to produce more useful output.

Codechange: Avoid emplace_back(new()) into a unique_ptr. (#11384)

This could theoretically leave an unmanaged pointer in certain circumstances, and directly using
make_unique shows intent.

Add: data parameter in Window::Close method.

This allows passing data when closing a window, e.g. to indicate how it was closed.

Codechange: Use begin/end of nwidget parts of begin/length.

This simplifies processing nwidget parts as, unlike the remaining length, the pointer to the end of the list never changes. This is the same principle as we use(d) for tracking end instead of length for C-style strings.

And this removes 160~ instances of the lengthof() macro.

Codechange: automatic adding of _t to (u)int types, and WChar to char32_t

for i in `find src -type f|grep -v 3rdparty/fmt|grep -v 3rdparty/catch2|grep -v 3rdparty/opengl|grep -v stdafx.h`; do sed 's/uint16& /uint16 \&/g;s/int8\([ >*),;[]\)/int8_t\1/g;s/int16\([ >*),;[]\)/int16_t\1/g;s/int32\([ >*),;[]\)/int32_t\1/g;s/int64\([ >*),;[]\)/int64_t\1/g;s/ uint32(/ uint32_t(/g;s/_uint8_t/_uint8/;s/Uint8_t/Uint8/;s/ft_int64_t/ft_int64/g;s/uint64$/uint64_t/;s/WChar/char32_t/g;s/char32_t char32_t/char32_t WChar/' -i $i; done

Codechange: Make DropDownListStringItem preformat and remove other implementations. (#11063)

Having to choose between DropDownListStringItem, DropDownListCharStringItem, and DropDownListParamStringItem depending on whether to draw a StringID, a raw string, or a StringID with extra parameters was needlessly complex.

Instead, allow passing a StringID or raw string to DropDownListStringItem. This will preformat the StringID into a raw string, and can therefore accept parameters via the normal SetDParam mechanism.

This also means that strings no longer need to be formatted on every draw.

Codechange: Use window parent association for dropdowns.

This replaces the separate window class and number properties, and
allows the window system to close dropdowns automatically.

Feature: opt-in survey when exiting a game

On first start-up, the game will ask if you want to participate
in our automated survey. You have to opt-in, and can easily opt-out
(via the Options) at any time.

When opt-in, whenever you exit a game, a JSON blob will be send
to the survey server hosted by OpenTTD. This JSON blob contains
information that gives a global picture of the game just played:
- What settings were used
- How many humans vs AIs
- How long the game has been played
- Basic information about the OS / CPU

All this information is kept very generic, so there is no
chance we send private information to our survey server.
Nothing in the JSON blob could identify you as a person; it
mostly tells about the game played. At any time you can see
what the JSON blob includes, by pressing the "Preview Survey
Results" button in-game.

Codechange: Use GetScrolled(Row/Item)FromWidget in more places.

In many instances the clicked row position is 'manually' calculated
instead of using the GetScrolledRowFromWidget helper function, with
variations on checks. Replace with the two helpers where possible.

Codechange: Scrollbar methods now accept size_t.

This clears up a lot of casts from size_t to int.

Codechange: migrate all Window-related timers to the new framework

This means we also say goodbye to GUITimers.

Change: Make all dropdown lists extend width if necessary.

This removes the auto_width parameter from ShowDropDown(At).

Change: Use Rect helpers for widget drawing.

This replaces repetitive and sometimes unwieldy use of constants.