Add support for custom role definitions

[heaths]

Once Azure/azure-rest-api-specs#11465 is checked in, regenerate source to support custom role definitions.

[sadasant]

This is code regeneration based on the latest swagger. One way to see the missing endopoints is to do an API comparison between Key Vault Admin on JS and on .Net.

[maorleger]

• Regenerate from swagger (and pin to sha instead of master)
• Get role definition
• Upsert role definition
• Delete custom role definition (ensure service error is nice)
• Consider properties bag vs splatting parameters - I need to see what it looks like
• Add custom role definition to sample
• Take a pass at existing samples since we've been making API changes

@heaths @sadasant is upsert the correct verb here? it's in the TS guidelines as an allowed verb but I wanted to double check (because we don't use upsert much outside of cosmos even though I personally think it makes sense and maps correctly to generate createOrUpdate method)

[heaths]

We don't have a verb for that in .NET. I asked the same thing in @christothes's .NET PR and asked @KrzysztofCwalina. Given the generated method is createOrUpdate and because that's what we used in the Search APIs, I'm leaning toward createOrUpdate. I mean, it's also the method description and is clearer to customers that want to create or update a method. Not everyone may know what "upsert" means.

That said, I understand there's a mix of both across services. Still, I maintain that "createOrUpdate" is more obvious than "upsert".