backends/igvm: Process initialization sections in IGVM file

backends/igvm: Process initialization sections in IGVM file

The initialization sections in IGVM files contain configuration that
should be applied to the guest platform before it is started. This
includes guest policy and other information that can affect the security
level and the startup measurement of a guest.

This commit introduces handling of the initialization sections during
processing of the IGVM file.

Signed-off-by: Roy Hopkins <roy.hopkins@randomman.co.uk>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Gerd Hoffman <kraxel@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/9de24fb5df402024b40cbe02de0b13faa7cb4d84.1751554099.git.roy.hopkins@randomman.co.uk
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>