[3.x] Rationalize property reversion

[RandomShaper]

Version of #46270 + #51173 + #51180 for 3.x.

[RandomShaper]

In the cherry-picked commit from 4.0, I've replaced the cases of #warning with WARN_PRINT_ONCE, to avoid errors in the CI. Moreover, given that they are about not-yet-implemented stuff, merging this PR would require tracking the progress of it in 4.0, to backport the missing pieces when they are available.

[akien-mga]

In the cherry-picked commit from 4.0, I've replaced the cases of #warning with WARN_PRINT_ONCE, to avoid errors in the CI. Moreover, given that they are about not-yet-implemented stuff, merging this PR would require tracking the progress of it in 4.0, to backport the missing pieces when they are available.

This needs to be implemented in this PR to be mergeable IMO. We used #warning in master for things that couldn't reasonably be implemented at the same time as the main feature that caused the need to implement them. But there's a big difference between 4.0.dev in master and 3.4.beta in 3.x in terms of expectations of stability and feature completeness.

[neikeq]

I was about to comment this but the diff changed and it seems inherits_script is no longer a thing? Here it is any way in case it may be of some use:

I haven't tested this code nor whether this PR breaks anything for C#, but this is probably how inherits_script should be implemented for C#:

bool CSharpScript::inherits_script(const Ref<Script> &p_script) const {
	if (!script_class)
		return false;
	Ref<CSharpScript> cs_script = p_script;
	if (cs_script.is_null())
		return false;
	if (!cs_script->script_class)
		return false;
	return cs_script->script_class->is_assignable_from(script_class);
}

[RandomShaper]

@neikeq, it changed indeed. I was in the middle of writing this comment.

UPDATES:

• This PR now also includes master's Fix up property reversion #51173.
• Instead of cherry-picking the Script::inherits_script() work from master, this now includes a simpler implementation, which doesn't include unimplemented functions. @neikeq, do you think it would be possible to write CSharpScript::get_base_script() as of now?

[neikeq]

It seems the new inherits_script cannot be overridden and relies on get_base_script, which is also not implemented for C#. In fact get_base_script is much harder to implement for C#, so if C# could override inherits_script that would be better.

[RandomShaper]

I see. I'll go back to the former way. Thank you.

[RandomShaper]

@akien-mga, sorry for the stream of updates.

Since a showstopper for this PR was the lack of many implementations of inherits_script(), I've added the NativeScript one myself and cherry-picked the C# one. So, the only one missing at this point is the PluginScript one, which I don't think is a big issue. (If it is, please let me know, since I'm not very familiar with it and I may be missing some important consequences of that.)

With all the commits included here, this is fully aligned with master and should be ready to merge once #51173 and #51180 are validated.

[akien-mga]

Thanks!