[Infra] The Great VPR Pragma PR

[AlexandreSinger]

VPR is moving to a style that uses "#pragma once" instead of header gaurds. These are less error prone and may be slightly more performant.

Converted all of the header gaurds in VPR into pragma once's.

Also moved all pragma onces to the top of all header files to maintain a consistent style. It is a good idea to have them as the very first line in all header files.

While going through all header files, cleaned up any extra header includes which were including things they did not need.

[AlexandreSinger]

@soheilshahrouz Sorry for the larger PR. This PR moves all include files to use pragma once. Please review when you have a moment.

[soheilshahrouz]

Thanks Alex.

I left a few comments aboud inlucding header files from catch2. I think because catch2 is a submodule in this project, we should include its header files with double double quotation marks.

[AlexandreSinger]

@soheilshahrouz Thank you so much for your review. I would agree that header files that are included in the project should use double quotations, however library headers should use brackets.

In this case we should be using brackets since VTR actually includes Catch2 as system headers:

vtr-verilog-to-routing/libs/EXTERNAL/CMakeLists.txt

Lines 162 to 168 in 607788b

	# Some catch2 headers generate warnings, so treat them as system headers to suppress warnings
	target_include_directories(Catch2
	SYSTEM
	PUBLIC
	$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/libcatch2/src>
	$<INSTALL_INTERFACE:include>
	)

I am ok with being vetoed on this, I am not married to it, but I think using angle brackets is proper in this case. What do you think?

[AlexandreSinger]

@soheilshahrouz Ah! I see, I just looked at the code and what you are saying is that it already used double quotation marks and I added angle brackets justs on the ones I added. I understand why thats not good. I turned them into double quotation marks so this does not block the PR; however, we should eventually revisit this topic. Not urgent at all though.