HTML5 one click deploy button is always active, even if misconfigured

[akien-mga]

Godot version:
3.2 RC 3 and master (689db68)

OS/device including version:
Linux

Issue description:
The HTML5 one click deploy button is always visible if an HTML5 preset has been defined, even if the templates are missing or if it's misconfigured.

When clicking:

EditorRunNative should check EditorExportPlatform::can_export() for all platforms when deciding whether the platform's one click deploy button should be visible or not (in EditorRunNative::_notification() at NOTIFICATION_PROCESS most likely.

The hotfix done for Android in #35570 could then likely be partly reverted (the removal of the adb == "" check should still be valid though if there is no way anymore to trigger this code without passing can_export()).

Steps to reproduce:

• Create new project
• Add HTML5 preset

[markgarcia]

Don't we want at least a way to provide a message to the user? Maybe instead of hiding the button we just show the errors provided by can_export(). Or perhaps disable it and have a tooltip showing the error.

[maxbarrett9]

@jackbondpreston Hey, did you fix this issue in the editor_run_native.cpp file? I'm a new contributor and I want to try fixing this on my own branch for practice.

[akien-mga]

This is fixed in 4.0+.