lib: sbi: Add initial domain context management support

The domain context management component in OpenSBI provides basic CPU
context management routines for existing OpenSBI domain. As domain
extension, it was initially designed to facilitate the suspension
and resumption of domains, enabling secure domains to efficiently
share CPU resources.

The patch also provides an addition to the OpenSBI domain to provide
updates on hart-domain assignment and declarations of contexts within
the domain.

Signed-off-by: Qingyu Shang <2931013282@sjtu.edu.cn>
Reviewed-by: Yu Chien Peter Lin <peterlin@andestech.com>
Tested-by: Yu Chien Peter Lin <peterlin@andestech.com>
Reviewed-by: Anup Patel <anup@brainfault.org>