Add get_static_rp_config method and test

[bewing]

New method to retrieve PIM static RP configuration.

This is built around the EOS CLI parser, so I'm open to suggestions from other drivers on changing the return/output.

[dbarrosop]

Can we base this on the IETF model instead? If this can hold for 2-3 weeks we might be able to even launch this as part of the OpenConfig framework.

[bewing]

I don't have an issue with holding this.

[bewing]

For reference, the IETF model for static RPs:

{
    "pim": {
        "address-family": {
            "ipv4": {
                "address-family": "ipv4",
                "rp": {
                    "static-rp": {
                        "ipv4-rp": {
                            "192.0.2.1": {
                                "ipv4-address": "192.0.2.1",
                                "pim-sm": {
                                    "policy-name": "v4-sm-acl",
                                    "override": False,
                                    "priority": 0, # EOS ONLY
                                    "hash-mask-length": 30 # EOS ONLY
                                },
                                "pim-bidir": {
                                    "policy-name": "v4-bidir-acl",
                                    "override": False,
                                }
                            }
                        }
                    }
                }
            },
            "ipv6": {
                "address-family": "ipv6",
                "rp": {
                    "static-rp": {
                        "ipv6-rp": {
                            "2001:DB8::1": {
                                "ipv6-address": "2001:DB8::1",
                                "pim-sm": {
                                    "policy-name": "v6-sm-acl",
                                    "override": False,
                                },
                                "pim-bidir": {
                                    "policy-name": "v6-bidir-acl",
                                    "override": False,
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}

[mirceaulinic]

@bewing - what's the status here?