feat(Catalog Management): support plan_id on offering instances

[benbuchanan]

Updating the platform-services-go-sdk to support plan_id on offering instances

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Output from acceptance testing:

TF_ACC=1 go test $(go list ./... |grep -v 'vendor') -v -run testAccCheckIBMCmOfferingInstanceDataSourceConfig -timeout 700m
PASS

TF_ACC=1 go test $(go list ./... |grep -v 'vendor') -v -run testAccCheckIBMCmOfferingInstanceConfig -timeout 700m
PASS

[benbuchanan]

cc @hkantare

[hkantare]

@benbuchanan can you resolve conflicts