Update all headers to `.hpp`

[sea-bass]

After moveit/moveit2#3113, this repo should update all the MoveIt .h headers to .hpp.

Great chance for someone to help out here!

[CihatAltiparmak]

Hi, i want to help you out. For this, we should minimize warnings which is due to other non-updated repositories like moveit_task_constructor and moveit_visual_tools.

I've also sent PR of these repositories to remove obsolete headers. I believe it would be nice to merge below PRs before this PR. I've converted PRs to draft in case blindly merging, but feel free to convert to ready.

• Enhancement/use hpp for headers based on PR https://github.com/moveit/moveit2/pull/3113 moveit_visual_tools#147
• Enhancement/use hpp for headers based on PR https://github.com/moveit/moveit2/pull/3113 moveit_task_constructor#641

Finally, we should also think about not only updating headers but also updating documentation.

[CihatAltiparmak]

Let's close this out bc looks like it's successfully sorted out.