Support for custom CNI file name

[frozenprocess]

Description

This PR allows users to change the filename via installation manfiest.

example:

apiVersion: operator.tigera.io/v1
kind: Installation
metadata:
  name: default
spec:
  cni:
    type: Calico
    ipam:
      type: Calico
    confName: "00-calico.conflist"

Release Note

Installation manifest now allows users to change the CNI file name using the `confName` value under the subtree of `cni`.

For PR author

• Tests for change.
• [ x ] If changing pkg/apis/, run make gen-files
• [ x ] If changing versions, run make gen-versions

For PR reviewers

A note for code reviewers - all pull requests must have the following:

• Milestone set according to targeted release.
• Appropriate labels:
  • kind/bug if this is a bugfix.
  • kind/enhancement if this is a a new feature.
  • enterprise if this PR applies to Calico Enterprise only.