Add bounds checks to type conversions to resolve gosec G115 errors

[bstoll]

Add bounds checking to appease golangci-lint's gosec G115 checks.

Errors before changes:

docker run --rm -v $(pwd):/app -w /app golangci/golangci-lint:v1.61.0 golangci-lint run -v --config=.github/linters/.golangci.yml --max-issues-per-linter 0 --max-same-issues 0 --timeout 10m ./...
...
topo/node/drivenets/drivenets.go:105:20: G115: integer overflow conversion uint32 -> int32 (gosec)
                        InnerPort: int32(v.Inside),
                                        ^
topo/node/drivenets/drivenets.go:106:20: G115: integer overflow conversion uint32 -> int32 (gosec)
                        OuterPort: int32(k),
                                        ^
topo/node/openconfig/openconfig.go:108:20: G115: integer overflow conversion uint32 -> int32 (gosec)
                        InnerPort: int32(v.Inside),
                                        ^
topo/node/openconfig/openconfig.go:109:20: G115: integer overflow conversion uint32 -> int32 (gosec)
                        OuterPort: int32(k),
                                        ^
topo/node/keysight/keysight.go:66:14: G115: integer overflow conversion uint32 -> int32 (gosec)
                        In:  int32(svc.Inside),
                                  ^
topo/node/keysight/keysight.go:67:14: G115: integer overflow conversion uint32 -> int32 (gosec)
                        Out: int32(svc.Outside),
                                  ^
topo/node/arista/arista.go:186:29: G115: integer overflow conversion int -> int32 (gosec)
                        NumInterfaces:      int32(len(links)),
                                                 ^
topo/node/arista/arista.go:187:29: G115: integer overflow conversion uint32 -> int32 (gosec)
                        Sleep:              int32(config.GetSleep()),
                                                 ^
topo/node/arista/arista.go:199:15: G115: integer overflow conversion uint32 -> int32 (gosec)
                                In:  int32(service.Inside),
                                          ^
topo/node/arista/arista.go:200:15: G115: integer overflow conversion uint32 -> int32 (gosec)
                                Out: int32(service.Outside),
                                          ^
topo/node/arista/arista.go:210:23: G115: integer overflow conversion uint32 -> int32 (gosec)
                                        KeySize:    int32(ssCert.KeySize),
                                                         ^
topo/node/node.go:483:21: G115: integer overflow conversion uint32 -> int32 (gosec)
                        Port:       int32(k),
                                         ^
topo/node/node.go:484:21: G115: integer overflow conversion uint32 -> int32 (gosec)
                        NodePort:   int32(v.NodePort),
                                         ^