Make Director::getRunningScene() return the expected result for any type of scene switch when called from Node::onEnter()

[rh101]

Describe your changes

This PR addresses the issue described in issue #2798, where the return value of Director::getRunningScene() is not consistent between instant scene switches and transitions if called in onEnter() of the new (incoming) scene.

The value of getRunningScene() when called from onEnter() will now always be the new scene.

The value of getRunningScene() when called from onExit() will now also be the new scene.

Issue ticket number and link

#2798

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Axmol 3.x ------------------------------------------------------------

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[halx99]

Wrong target branch I guess, so I switch to release/2.x

[rh101]

Wrong target branch I guess, so I switch to release/2.x

Sorry, yes, it should have been release/2.x. Thank you for fixing it