Document Mono-specific classes

This fully documents all Mono-specific classes.

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Fix a random crash in the TileSet editor

Restore previous mouse position when leaving the editor freelook mode

Occurred when selecting polygon collision mode, then drawing a single point, then selecting rectangle mode, and finally trying to select a rectangle.

- Remove the crosshair as it no longer serves a purpose (the cursor will
  now appear where the user "expects" it to).

This closes https://github.com/godotengine/godot-proposals/issues/1076.

GDScript debugger incorrect error line fixed

if the first line of an else or an elif throws a runtime error the
debugger shows incorrect line number.

DocData: Skip language-specific ClassDoc without methods/constants

Removes the useless `@C#`, `@NativeScript` and `@VisualScript` entries.

Simplify and fix Transform2D get_rotation

Fix code editor Replace tool to work with 'Selection Only' option

Allow Godot to kill its own PID

Expose disable_render_loop property to GDScript

Clean up the GodotPlugin public API

Ensures that when the `Selection Only` option is selected, the Replace
tool replaces occurrences of the search phrase only within the selected
region, and in order of occurrence.

Added shadowed var warning for `for` loop counter

Bind Shape2D draw method

Add a suffix to the window title when running from a debug build

Allow duplicating files when holding Control

Display freelook speed and zoom in units in the 3D editor viewport

Normalise p_up_direction vector in move_and_slide()

Since projects started from the editor or exported in debug mode
run slower than those exported in release mode, this should be
clearly presented to the user.

This partially addresses #20219.

move_and_slide_with_snap() and fix tolerance in
move_and_slide_with_snap() max floor angle.

Now that the 3D editor grid is infinite and adjusts its step automatically,
this helps people get a better sense of scale when moving around in the
3D viewport.

This also fixes the indicator bar drawing on hiDPI displays.

Check pointers against nullptr.

Use path instead classname to prevent errors for exported visual shaders

C#: Add Visual Studio support

Skeleton and Skeleton inspector low-level changes

GDScript debugger stepping to incorrect line fix

Fix: Ctrl + Click not working for subclasses

Link exposed setters/getters in property descriptions

Change in-editor documentation style to match online docs.

Unify OS.get_system_time_* and OS.get_unix_time