update and rebase to QEMU v6.1.0

Very clean rebase, only the +pve version handling needed manual fixing.
Drops two applied patches from extra/ and adds one new from upstream
(extra/0001*, fixes VNC over unix sockets) as well as 3 of my own for
allowing password changes on custom VNC displays again (as seen and
reviewed upstream, but not yet applied).

Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>

debian/patches/pve/0004-PVE-Config-ui-spice-default-to-pve-certificates.patch

@@ -9,7 +9,7 @@ Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
  1 file changed, 9 insertions(+), 6 deletions(-)
 
 diff --git a/ui/spice-core.c b/ui/spice-core.c
-index 272d19b0c1..9719214f19 100644
+index 0371055e6c..840cf56923 100644
 --- a/ui/spice-core.c
 +++ b/ui/spice-core.c
 @@ -694,32 +694,35 @@ static void qemu_spice_init(void)