Report memory used and swap used in worker res

Attempting to report "memory used by other processes" in the MemReserved
field fails to take into account the fact that the system's memory used
includes memory used by ongoing tasks.

To properly account for this, worker should report the memory and swap
used, then the scheduler that is aware of the memory requirements for a
task can determine if there is sufficient memory available for a task.

api/docgen/docgen.go

@@ -231,8 +231,9 @@ func init() {
 				Hostname: "host",
 				Resources: storiface.WorkerResources{
 					MemPhysical: 256 << 30,
+					MemUsed:     2 << 30,
 					MemSwap:     120 << 30,
-					MemReserved: 2 << 30,
+					MemSwapUsed: 2 << 30,
 					CPUs:        64,
 					GPUs:        []string{"aGPU 1337"},
 				},

api/version.go

@@ -58,7 +58,7 @@ var (
 	FullAPIVersion1 = newVer(2, 1, 0)
 
 	MinerAPIVersion0  = newVer(1, 2, 0)
-	WorkerAPIVersion0 = newVer(1, 1, 0)
+	WorkerAPIVersion0 = newVer(1, 2, 0)
 )
 
 //nolint:varcheck,deadcode