Add UPnP support (port forwarding, querying external IP)

Fix LWSPeer get_connected_[host/port]

allow undefined GODOT_DEBUG_MSBUILD environment  variable

Show opened script or help name

(cherry picked from commit e8bfc09b81f02395226a06f5a8ecd47bea136cc6)

(cherry picked from commit 74808e71d213888d40671246ace3c701dd674a2b)

Mono fixes and improvements

- Add option to print MSBuild's stdout and stderr instead of redirecting it. This can be enabled by setting the environment variable: Godot_DEBUG_MSBUILD=1

[Inspector] Fix search field losing focus when typing

Fixes #19383.

Fix #19382

Set SO_BROADCAST socket option for UDP sockets.

Revert "Prevent visibility notification from being called twice in object creation"

Fixes ObjectDB leak printout with mono.

Fix Rect2 properties typo

Add option to disable automatic multiplayer poll in SceneTree

Automatic poll from SceneTree is enabled by default.
This allows for polling (and thus RPCs/RSETs) manually in other loops
(e.g. physics, thread, specific step) and for proper mutex protecion
when accessing the multiplayer API from threads (e.g. for sending larger
files in chunks).

Fix Mono static linking on Mingw

Minor changes to the Scene and Canvas editors' tooltips

Add cli paramerter --check-only for script parsing

Fix return type of isnan and isinf in the shader language

Fix return type of _get() virtual method

This reverts commit 4d277b96.

Woops, this wasn't meant to be committed. I just reverted it locally
to test something, nothing wrong with the original commit :)

Fixes godotengine/godot-docs#1486.

This reverts commit d42b1760.