i386/tdx: Support user configurable mrconfigid/mrowner/mrownerconfig

i386/tdx: Support user configurable mrconfigid/mrowner/mrownerconfig

Three sha384 hash values, mrconfigid, mrowner and mrownerconfig, of a TD
can be provided for TDX attestation. Detailed meaning of them can be
found: https://lore.kernel.org/qemu-devel/31d6dbc1-f453-4cef-ab08-4813f4e0ff92@intel.com/

Allow user to specify those values via property mrconfigid, mrowner and
mrownerconfig. They are all in base64 format.

example
-object tdx-guest, \
  mrconfigid=ASNFZ4mrze8BI0VniavN7wEjRWeJq83vASNFZ4mrze8BI0VniavN7wEjRWeJq83v,\
  mrowner=ASNFZ4mrze8BI0VniavN7wEjRWeJq83vASNFZ4mrze8BI0VniavN7wEjRWeJq83v,\
  mrownerconfig=ASNFZ4mrze8BI0VniavN7wEjRWeJq83vASNFZ4mrze8BI0VniavN7wEjRWeJq83v

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250508150002.689633-14-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>