Scrolling, Focus, Combo: fixed SetKeyboardFocusHere()/SetItemDefaultFocus()/ScrollToRectEx() during an appearing form not centering item. (#5902, #2812, #4242, #2900)

Amend 44f80118 and 8f495e55

(initialize WGPUCompareFunction params to valid values)

Drag and Drop: fixed GetDragDropPayload() returning a non-NULL value before payload is submitted.  (#5910, #143)

+ Added test "widgets_dragdrop_new_payloads" in Test Suite.

Layout: fixed End()/EndChild() incorrectly asserting if users manipulates cursor position inside a collapsed/culled window and IMGUI_DISABLE_OBSOLETE_FUNCTIONS is enabled. (#5548, #5911)

Amend 54fb051e
+ Internals: added IsKeyboardKey(), IsMouseKey() helpers.

Inputs: fixed moving a window or drag and dropping from preventing input-owner-unaware code from accessing keys. (#5888, #4921, #456)

Amend 4448d975. This is more consistent with input owner design.

Amend change of SetActiveIdUsingAllKeyboardKeys() in 4448d975 which seemingly accidentally reverted the change intended by fd408c97

Which makes it easier to hook/disable those keys from outside if needed.

+ fix warning from a582d92c

Inputs: refacotr/extract CalcRoutingScore() out of SetShortcutRouting(), easier to follow with early returns.

+ clarified comments about GetMouseCursor() #5739

Backends: OpenGL3: Reverted use of glBufferSubData(). (#4468, #4504, #3381, #2981, #4825, #4832, #5127)

One idea being that this value can be easily locked (for blind menus) or manipulated (for queries from outside).

- and ImGuiInputFlags_RouteUnlessBgFocused
- will be useful for blind menu handlers.

Inputs: added wip/experiment routing system: Shortcut(), RoutingFocused policy, SetShortcutRouting(). (#456, #2637, #3724)

- InputText() uses Shortcut().

Note the removed comments (hence not squashing)
Amend 4448d975
(#456, #2637, #2620, #2891, #3370,, #4828, #5108, #5242, #5641)

Inputs: added wip/internal Input Owner system. (#456, #2637, #2620, #2891, #3370, #4828, #5108, #5242, #5641)

- Added SetKeyOwner(), SetItemKeyOwner(), TestKeyOwner().
- Added new IsKeyXXX IsMouseXXX functions with ImGuID owner_id and flags.
- Obsoleted SetItemUsingMouseWheel(). (#2891)
- Removed IsKeyPresseedEx() which was a recent internal addition 2022-07-08 deemed to be temporary exactly for this.
- Added ImGuiButtonFlags_NoSetKeyOwner, ImGuiButtonFlags_NoTestKeyOwner
- Added ImGuiSelectableFlags_NoSetKeyOwner.
- Added ImGuiInputFlags_LockThisFrame, ImGuiInputFlags_LockUntilRelease for for SetKeyOwner(), SetItemKeyOwner().
- Added ImGuiInputFlags_CondXXX values for SetItemKeyOwner().

Debug Tools: Added DebugLocateItem()/DebugLocateItemOnHover() to visually locate items when hovering a 0xXXXXXXXX value. (#5855, #2673, #4631)

Internals: rework FocusScope system, current scope doesn't need to be in window + child doesn't inherit.

Intended as part of work for input routing + blind menu processing shortcuts. Some of this commit will be stripped by next commit.
Intent was to sort windows along with focus scope to build a hierarchy, but for our needs we'd need a persistant one, so scrapping the idea. Not squashing this with next commit to keep a bit of history for future references.

Examples: Android: Using LoadIniSettingsFromMemory() / SaveIniSettingsToMemory() to save in appropriate location for Android. (#5836)

IO: Clear AppFocusLost in EndFrame() in order to allow backend or application code to poll and react to it

+ Amend a241dc79 with the same clearing of MouseDownDuration[] as keyboard ones.

Commented out redirecting OpenPopupContextItem() which was briefly the name of OpenPopupOnItemClick() from 1.77 to 1.79.