Speed limit controller

Added toggle to control the cruise set speed according to speed limit supplied by OSM, NOO, or the vehicle itself.

Co-Authored-By: Jacob Pfeifer <jacob@pfeifer.dev>
Co-Authored-By: Efini <19368997+efini@users.noreply.github.com>
Co-Authored-By: Kumar <36933347+rav4kumar@users.noreply.github.com>
Co-Authored-By: Jason Wen <haibin.wen3@gmail.com>

cereal/car.capnp

@@ -126,6 +126,7 @@ struct CarEvent @0x9b1657f34caf3ad3 {
     noLaneAvailable @127;
     openpilotCrashed @128;
     pedalInterceptorNoBrake @130;
+    speedLimitChanged @131;
     torqueNNLoad @132;
 
     radarCanErrorDEPRECATED @15;

cereal/custom.capnp

@@ -10,6 +10,7 @@ $Cxx.namespace("cereal");
 # you can rename the struct, but don't change the identifier
 struct FrogPilotCarControl @0x81c2f05a394cf4af {
   alwaysOnLateral @0 :Bool;
+  speedLimitChanged @1 :Bool;
 }
 
 struct FrogPilotDeviceState @0xaedffd8f31e7b55d {
@@ -31,7 +32,12 @@ struct FrogPilotPlan @0xda96579883444c35 {
   redLight @5 :Bool;
   safeObstacleDistance @6 :Int16;
   safeObstacleDistanceStock @7 :Int16;
+  slcOverridden @8 :Bool;
+  slcOverriddenSpeed @9 :Float64;
+  slcSpeedLimit @10 :Float64;
+  slcSpeedLimitOffset @11 :Float32;
   stoppedEquivalenceFactor @12 :Int16;
+  unconfirmedSlcSpeedLimit @13 :Float64;
 }
 
 struct CustomReserved4 @0x80ae746ee2596b11 {