feat: add inline volume support

[andyzhangx]

What type of PR is this?
/kind feature

What this PR does / why we need it:
feat: add inline volume support
uesr could still set --set feature.enableInlineVolume=false to disable inline volume support in chart install.

Which issue(s) this PR fixes:

Fixes #148

Special notes for your reviewer:
feat: add inline volume support

kind: Pod
apiVersion: v1
metadata:
  name: nginx-pod-inline-volume
spec:
  nodeSelector:
    "kubernetes.io/os": linux
  containers:
    - image: mcr.microsoft.com/oss/nginx/nginx:1.19.5
      name: nginx-nfs
      command:
        - "/bin/bash"
        - "-c"
        - set -euo pipefail; while true; do echo $(date) >> /mnt/nfs/outfile; sleep 1; done
      volumeMounts:
        - name: persistent-storage
          mountPath: "/mnt/nfs"
  volumes:
    - name: persistent-storage
      csi:
        driver: nfs.csi.k8s.io
        volumeAttributes:
          server: nfs-server.default.svc.cluster.local  # required
          share: /  # required
          mountOptions: "nfsvers=4.1,sec=sys"  # optional

Does this PR introduce a user-facing change?:

feat: add inline volume support

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: andyzhangx

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• OWNERS [andyzhangx]

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[coveralls]

Pull Request Test Coverage Report for Build 1682798475

• 6 of 10 (60.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.4%) to 77.716%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/nfs/nodeserver.go	6	10	60.0%

Totals
Change from base Build 1670104364:	-0.4%
Covered Lines:	558
Relevant Lines:	718

---

💛 - Coveralls

[kfox1111]

Looks pretty good to me. Two possible tweaks:

1. It may be good to default this feature to off rather then on. This would better align with the PodSecurity design. You'd need to enable the feature and add additional k8s policy to enable it safely. Consciously having to enable gives the opportunity to remind the user about the policy need.
2. support for mount options. For example: nfsvers=4.2

[andyzhangx]

Looks pretty good to me. Two possible tweaks:

1. It may be good to default this feature to off rather then on. This would better align with the PodSecurity design. You'd need to enable the feature and add additional k8s policy to enable it safely. Consciously having to enable gives the opportunity to remind the user about the policy need.
2. support for mount options. For example: nfsvers=4.2

@kfox1111 it's done, PTAL, thanks. added a new parameter as csi.volumeAttributes.mountOptions

  volumes:
    - name: persistent-storage
      csi:
        driver: nfs.csi.k8s.io
        volumeAttributes:
          server: nfs-server.default.svc.cluster.local  # required
          share: /  # required
          mountOptions: "nfsvers=4.1,sec=sys"  # optional

[kfox1111]

Looks good to me. Thanks! :)