Describe supported extensions per active domain

[sameo]

The SUPD active domain enumeration function describes which supervisor domains are active. But active domains may or may not support CoVE and there is no way for SW to get that information, aside from poking at extensions specific functions like e.g. sbi_covh_get_tsm_info or CoVE.

Would it make sense to add a sbi_spud_supported_extensions() function to let a supervisor domain manager describe which supervisor domain ID addressable (as defined in https://github.com/riscv-non-isa/riscv-ap-tee/blob/main/src/sbi_cove.adoc#function-enumerate-active-supervisor-domains-fid-0) SBI extensions it supports? It would return a 64-bit value with all supported extensions, and CoVE could reserve bit 0.