Adds support for GICv5 as both a host and guest. Additionally, on platforms with
FEAT_GICE_LEGACY, supports a GICv3 guest under a GICv5 host.
The current implementation only implements the IRS component. The ITS is not
currently emulated, which prevents the use of MSIs.
Co-developed-by: Andrew Turner <andrew@FreeBSD.org>
Sponsored by: Arm Ltd