feature(ingress-nginx):Add ImplementationSpecific path support

[obukhovaa]

What type of PR is this?

/kind feature

What this PR does / why we need it:
Implemented support for ImplementationSpecific path type in the ingress-nginx provider, currently it fails with error when converting ingress resource.

Does this PR introduce a user-facing change?:

Implemented support for ImplementationSpecific path type in the ingress-nginx provider

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: obukhovaa
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[k8s-ci-robot]

Hi @obukhovaa. Thanks for your PR.

I'm waiting for a github.com member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[Stevenjin8]

This is only true if `nginx.ingress.kubernetes.io/use-regex: "true"