Create Events when scaling down YB-TServers

[bhavin192]

Creates two events, ScalingDownTServers and ScaledDownTServers. These events get displayed when kubectl describe ybcluster command is executed.

Scenarios tested

• Tried creating a new ybcluster.
• Scaled down the TServers replica count from 4 to 3.

• The events were visible in the Events section of kubectl describe ybclusters -nyb-operator example-ybcluster.

  $ kubectl describe ybclusters.yugabyte.com -nyb-operator example-ybcluster
  Name:         example-ybcluster
  Namespace:    yb-operator
  Labels:       <none>
  Annotations:  API Version:  yugabyte.com/v1alpha1
  Kind:         YBCluster
  …
  Events:
    Type     Reason               Age                 From                  Message
    ----     ------               ----                ----                  -------
    Warning  ScalingDownTServers  14m (x14 over 14m)  ybcluster-controller  Scaling down TServers to 3: waiting for data move to complete
    Normal   ScaledDownTServers   13m                 ybcluster-controller  Scaled down TServers successfully      

[nchandrappa]

@bhavin192 Code looks good. Please add a test or update test in func TestReconcile(t *testing.T) for testing the new events. Thanks.

[bhavin192]

Hey @nchandrappa right now few of the tests are broken due to other changes we have made previously (using exec API). And TestReconcile is one of the broken tests. I'm planning to work on them as a separate PR as it involves more efforts. I will cover this event related change in the updated tests later.

[nchandrappa]

@bhavin192 okay then I'll approve the PR. Please add those tests when you get a chance. Thanks