Changing API style guide not to use acronyms

[wora]

Using acronyms in API definition has been a very debatable issue, such as HTTPRequest vs HttpRequest, and different programming language made different choice. For Istio, two heavily used languages, Go and proto3, made different choice.

Go: https://github.com/kubernetes/community/blob/master/contributors/devel/api-conventions.md#naming-conventions

Acronyms should similarly only be used when extremely commonly known. All letters in the acronym should have the same case, using the appropriate case for the situation. For example, at the beginning of a field name, the acronym should be all lowercase, such as "httpGet". Where used as a constant, all letters should be uppercase, such as "TCP" or "UDP".

proto3 style strictly use camel case for type names, no acronym is allowed.

One important issue is proto3 field names are using lower_underscore_case. When field names are used in JSON, they are mechanically converted to lowerCamelCase, so acronyms are not possible.

Given the above differences and all Istio APIs are written in proto3, I recommend Istio should use CamelCase without acronyms. This would be consistent with Envoy, proto3, gRPC. Currently, only HTTP, TLS, TCP and a few acronyms are used, so this would not be a major change.

@rshriram I think this proposal would mainly impact your work. Other places should be fine. In the long term, aligning all proto3 APIs is more valuable than aligning proto3 with Go. Thanks.