oversubscription: adds CLI and API support

This commit updates the API to pass the MemoryMaxMB field, and the CLI to show
the max set for the task.

Also, start parsing the MemoryMaxMB in hcl2, as it's set by tags.

A sample CLI output; note the additional `Max: ` for "task":

```
$ nomad alloc status 96fbeb0b
ID                  = 96fbeb0b-a0b3-aa95-62bf-b8a39492fd5c
[...]

Task "cgroup-fetcher" is "running"
Task Resources
CPU        Memory         Disk     Addresses
0/500 MHz  32 MiB/20 MiB  300 MiB

Task Events:
[...]

Task "task" is "running"
Task Resources
CPU        Memory          Disk     Addresses
0/500 MHz  176 KiB/20 MiB  300 MiB
           Max: 30 MiB

Task Events:
[...]
```

command/agent/job_endpoint.go

@@ -1193,6 +1193,10 @@ func ApiResourcesToStructs(in *api.Resources) *structs.Resources {
 		out.Cores = *in.Cores
 	}
 
+	if in.MemoryMaxMB != nil {
+		out.MemoryMaxMB = *in.MemoryMaxMB
+	}
+
 	// COMPAT(0.10): Only being used to issue warnings
 	if in.IOPS != nil {
 		out.IOPS = *in.IOPS

command/agent/job_endpoint_test.go

@@ -2930,6 +2930,53 @@ func TestConversion_apiLogConfigToStructs(t *testing.T) {
 	}))
 }
 
+func TestConversion_apiResourcesToStructs(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		name     string
+		input    *api.Resources
+		expected *structs.Resources
+	}{
+		{
+			"nil",
+			nil,
+			nil,
+		},
+		{
+			"plain",
+			&api.Resources{
+				CPU:      helper.IntToPtr(100),
+				MemoryMB: helper.IntToPtr(200),
+			},
+			&structs.Resources{
+				CPU:      100,
+				MemoryMB: 200,
+			},
+		},
+		{
+			"with memory max",
+			&api.Resources{
+				CPU:         helper.IntToPtr(100),
+				MemoryMB:    helper.IntToPtr(200),
+				MemoryMaxMB: helper.IntToPtr(300),
+			},
+			&structs.Resources{
+				CPU:         100,
+				MemoryMB:    200,
+				MemoryMaxMB: 300,
+			},
+		},
+	}
+
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			found := ApiResourcesToStructs(c.input)
+			require.Equal(t, c.expected, found)
+		})
+	}
+}
+
 func TestConversion_apiConnectSidecarTaskToStructs(t *testing.T) {
 	t.Parallel()
 	require.Nil(t, apiConnectSidecarTaskToStructs(nil))

command/alloc_status.go

@@ -563,13 +563,21 @@ func (c *AllocStatusCommand) outputTaskResources(alloc *api.Allocation, task str
 	var resourcesOutput []string
 	resourcesOutput = append(resourcesOutput, "CPU|Memory|Disk|Addresses")
 	firstAddr := ""
+	secondAddr := ""
 	if len(addr) > 0 {
 		firstAddr = addr[0]
 	}
+	if len(addr) > 1 {
+		secondAddr = addr[1]
+	}
 
 	// Display the rolled up stats. If possible prefer the live statistics
 	cpuUsage := strconv.Itoa(*resource.CPU)
 	memUsage := humanize.IBytes(uint64(*resource.MemoryMB * bytesPerMegabyte))
+	memMax := ""
+	if max := resource.MemoryMaxMB; max != nil && *max != 0 && *max != *resource.MemoryMB {
+		memMax = "Max: " + humanize.IBytes(uint64(*resource.MemoryMaxMB*bytesPerMegabyte))
+	}
 	var deviceStats []*api.DeviceGroupStats
 
 	if stats != nil {
@@ -588,7 +596,10 @@ func (c *AllocStatusCommand) outputTaskResources(alloc *api.Allocation, task str
 		memUsage,
 		humanize.IBytes(uint64(*alloc.Resources.DiskMB*bytesPerMegabyte)),
 		firstAddr))
-	for i := 1; i < len(addr); i++ {
+	if memMax != "" || secondAddr != "" {
+		resourcesOutput = append(resourcesOutput, fmt.Sprintf("|%v||%v", memMax, secondAddr))
+	}
+	for i := 2; i < len(addr); i++ {
 		resourcesOutput = append(resourcesOutput, fmt.Sprintf("|||%v", addr[i]))
 	}
 	c.Ui.Output(formatListWithSpaces(resourcesOutput))