builtin/k8s: Allow for defined resource limits for pods

[briancain]

This pull request introduces the ability to define resource limits for pods during deployment.

Tested with https://github.com/hashicorp/waypoint-examples/tree/main/kubernetes/nodejs

diff --git a/kubernetes/nodejs/waypoint.hcl b/kubernetes/nodejs/waypoint.hcl
index d3eb818..67ef4da 100644
--- a/kubernetes/nodejs/waypoint.hcl
+++ b/kubernetes/nodejs/waypoint.hcl
@@ -20,6 +20,13 @@ app "example-nodejs" {
   deploy {
     use "kubernetes" {
       probe_path = "/"
+
+      resources = {
+        limits_cpu = "500m"
+        limits_memory = "512Mi"
+        request_cpu = "100m"
+        request_memory = "256Mi"
+      }
     }
   }

After a waypoint up, describing the pod deployed you can see the resources are updated:

Containers:
  example-nodejs-01ex7nsq75ndyevxqrxajqb4rq:
    Container ID:
    Image:          example-nodejs:1
    Image ID:
    Port:           3000/TCP
    Host Port:      0/TCP
    State:          Waiting
      Reason:       ErrImagePull
    Ready:          False
    Restart Count:  0
    Limits:
      cpu:     500m
      memory:  512Mi
    Requests:
      cpu:      500m
      memory:   512Mi

Fixes #677

[krantzinator]

👏🏻