[Core]create internal module for thridparty system compatible building

[ashione]

Exporting internal module

Related issue number

Closes #44065

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• Testing Strategy
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[larrylian]

@jjyao
internal.cc/internal.h and exported_internal has been removed in this PR #34697 (Because it was thought to be unused. However, in reality, Mobius is using it.）

Now it block build the mobius project update ray version (old version -> ray lastest 2.9.3) ray-project/mobius#60 .
I think we should merge this revert PR first, to support the Mobius upgrade of the Ray version.

[ashione]

@robertnishihara @raulchen @SongGuyang Anyone can take over ray core module management? Seems no one can go on developing.

[SongGuyang]

Seems that the exported internal flags were deleted accidentally. I will merge this PR if there are no more other comments.

[jjyao]

Can we add these code to mobius repo?

We should add some comment saying that the code is used by an external repo otherwise it's guaranteed to be removed in the future by someone without context.

[ashione]

Can we add these code to mobius repo?

We should add some comment saying that the code is used by an external repo otherwise it's guaranteed to be removed in the future by someone without context.

Thirdparty can not decide what symbols ray should be exported? Usually opensource system made it in main repo.

[jjyao]

Can you add comments to the code saying where it's used so people don't accidentally delete it again in the future?

[ashione]

Can you add comments to the code saying where it's used so people don't accidentally delete it again in the future?

Comments had been added in internal header file.