[BugFix][C++] Remove arrow header from GraphAr's header

[acezen]

Proposed changes

commit-49685 has include arrow header into graphar' header which we should not do that. Because we can't assume that users's system installed arrow.

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Further comments

Fixed #228

[acezen]

hi, @Ziy1-Tan, this pull request needs your review

[lixueclaire]

LGTM

[Ziy1-Tan]

hi, @Ziy1-Tan, this pull request needs your review

I have a little doubt. When arrow is not installed, cmake will automatically build from source code. So we can always guarantee that arrow is installed, right?

[Ziy1-Tan]

shared_ptr requires a full definition of the type, so the forward declaration does not work

[acezen]

hi, @Ziy1-Tan, this pull request needs your review

I have a little doubt. When arrow is not installed, cmake will automatically build from source code. So we can always guarantee that arrow is installed, right?

the source-build arrow is just used by graphar and include by static library(not expose), it does not install to system, so when user use graphar, we should guarantee they can run with graphar without arrow installed.

[acezen]

shared_ptr requires a full definition of the type, so the forward declaration does not work

Actually, shared_ptr can work with forward declaration.
https://stackoverflow.com/questions/16588075/forward-declarations-and-shared-ptr

[acezen]

This PR still need some refine, like revise the Expression as a real wrapper of arrow::Expression which not expose the arrow::Expression outside.