Bug 31356: Bump protover for new padding machines

By binding the protover numbering to specific padding machines, we can make
our padding negotiation simpler. We probably should have done this in the
first place.

This has the side effect that earlier 0.4.1.x-alpha clients won't negotiate
with 0.4.1.x-stable relays, and 0.4.1.x-stable clients won't negotiate with
earlier 0.4.1.x-alpha relays (or 0.4.0.x relays). Since we don't support
alphas after the stable is released, this is fine, so long as it gets in
before the first stable of 0.4.1.x.

src/core/or/protover.c

@@ -402,7 +402,7 @@ protover_get_supported_protocols(void)
 #endif
     "Microdesc=1-2 "
     "Relay=1-2 "
-    "Padding=1 "
+    "Padding=2 "
     "FlowCtrl=1";
 }
 

src/rust/protover/protover.rs

@@ -168,7 +168,7 @@ pub(crate) fn get_supported_protocols_cstr() -> &'static CStr {
              LinkAuth=3 \
              Microdesc=1-2 \
              Relay=1-2 \
-             Padding=1 \
+             Padding=2 \
              FlowCtrl=1"
         )
     } else {
@@ -183,7 +183,7 @@ pub(crate) fn get_supported_protocols_cstr() -> &'static CStr {
              LinkAuth=1,3 \
              Microdesc=1-2 \
              Relay=1-2 \
-             Padding=1 \
+             Padding=2 \
              FlowCtrl=1"
         )
     }