### Feature

- ACTION REQUIRED : In CoreDNS v1.7.0, [metrics names have been changed](https://github.com/coredns/coredns/blob/master/notes/coredns-1.7.0.md#metric-changes) which will be backward incompatible with existing reporting formulas that use the old metrics' names. Adjust your formulas to the new names before upgrading. 
  
  Kubeadm now includes CoreDNS version v1.7.0. Some of the major changes include:

  // HTTPGet specifies the http request to perform.
  // +optional
  optional HTTPGetAction httpGet = 2;

  // Deprecated. TCPSocket is NOT supported as a LifecycleHandler and kept
  // for the backward compatibility. There are no validation of this field and
  // lifecycle hooks will fail in runtime when tcp handler is specified.
  // +optional
  optional TCPSocketAction tcpSocket = 3;
}

imaginary_lit = (decimal_digits | int_lit | float_lit) "i" .
</pre>

<p>
For backward compatibility, an imaginary literal's integer part consisting
entirely of decimal digits (and possibly underscores) is considered a decimal
integer, even if it starts with a leading <code>0</code>.
</p>

<pre>
0i
0123i         // == 123i for backward-compatibility
0o123i        // == 0o123 * 1i == 83i
0xabci        // == 0xabc * 1i == 2748i

  
  Having appropriate QueueingHintFn contributes to reducing useless retries and thus improves the overall scheduler's performance.
  
  **How can I migrate?**
  
  For backward compatibility, nil `QueueingHintFn` is treated as always returning QueueAfterBackoff. 
  So, if you want to just keep the existing behavior, you can register `ClusterEventWithHint` with no `QueueingHintFn` in it. 

    * Add metrics `*_admission_latencies_milliseconds` and `*_admission_latencies_milliseconds_summary` for backward compatible, but will be removed in a future release.

* For Deployment, ReplicaSet, and DaemonSet, selectors are now immutable when updating via the new `apps/v1beta2` API. For backward compatibility, selectors can still be changed when updating via `apps/v1beta1` or `extensions/v1beta1`. ([#50719](https://github.com/kubernetes/kubernetes/pull/50719), [@crimsonfaith91](https://github.com/crimsonfaith91))

- Dropped the additional rule requirement (cronjobs/finalizers) for roles
  using kubectl create cronjobs to ensure backward compatibility. ([#124883](https://github.com/kubernetes/kubernetes/pull/124883), [@ardaguclu](https://github.com/ardaguclu))

* Update gogo/protobuf to serialize backward, as to get better performance on deep objects. ([#77355](https://github.com/kubernetes/kubernetes/pull/77355), [@apelisse](https://github.com/apelisse))

`$enable-hover-media-query` are deprecated.\n//\n// Originally added during our alphas and maintained during betas, this mixin was\n// designed to prevent `:hover` stickiness on iOS-an issue where hover styles\n// would persist after initial touch.\n//\n// For backward compatibility, we've kept these mixins and updated them to\n// always return their regular pseudo-classes instead of a shimmed media query.\n//\n// Issue: https://github.com/twbs/bootstrap/issues/25195\n\n@mixin hover() {\n  &:hover { @content; }\n}\n\n@mixin...

`$enable-hover-media-query` are deprecated.\n//\n// Originally added during our alphas and maintained during betas, this mixin was\n// designed to prevent `:hover` stickiness on iOS-an issue where hover styles\n// would persist after initial touch.\n//\n// For backward compatibility, we've kept these mixins and updated them to\n// always return their regular pseudo-classes instead of a shimmed media query.\n//\n// Issue: https://github.com/twbs/bootstrap/issues/25195\n\n@mixin hover() {\n  &:hover { @content; }\n}\n\n@mixin...