calico add support for container ip forwarding setting

[zhengtianbao]

What type of PR is this?

/kind feature

What this PR does / why we need it:

In some scenarios, calico should enable allow ip forwarding in container setting.
refer: https://docs.projectcalico.org/reference/cni-plugin/configuration#container-settings

It allows IP forwarding inside containers:

https://github.com/projectcalico/cni-plugin/blob/1e4e077b9bce26a4c8116b6359e200c7e95b85e3/pkg/dataplane/linux/dataplane_linux.go?_pjax=%23js-repo-pjax-container%2C%20div%5Bitemtype%3D%22http%3A%2F%2Fschema.org%2FSoftwareSourceCode%22%5D%20main%2C%20%5Bdata-pjax-container%5D#L444-L475

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[Calico] Add support for container ip forwarding setting, using new variable `calico_allow_ip_forwarding`

[k8s-ci-robot]

Hi @zhengtianbao. Thanks for your PR.

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[floryut]

👍

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: floryut, zhengtianbao

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[floryut]

/ok-to-test

[liupeng0518]

/lgtm