✨ Extend OpenQASM-to-QC translation

[denialhaag]

#1671 has added an initial translation from OpenQASM to the QC dialect. The translation does not yet support all features of OpenQASM.

This issue collects all features we should support. It is expected to grow in the future.

• Add support for duration type
• Add support for opaque gate declarations
• Improve support for include statement (currently, only stdgates.inc and qelib1.inc are supported)

Important

Please break out sub-issues as needed when implementing certain bullet points.

[MatthiasReumann]

Regarding the support of the scf.while operations, I just had a really interesting conversation with Gemini:

Apparently, the go-to way to translate a while loop to the (rather complex) scf.while operation is to convert the while to the cf dialect and then use the lift-cf-to-scf pass to create the scf.while operation. This lifting procedure will (probably) always work for frontends such as OpenQASM because their while loop specification is rather cleverly chosen. The person addressing this issue might want to investigate this further. Looking at Polygeist might be worthwhile.

[burgholzer]

With the exception of #2289, none of these should be blockers for v4.0. Moving this to the 4.1 milestone.