Client proxy webhook rule

[HaoYang0000]

1. client proxy annotation "vertica.com/use-client-proxy: "true""
   cannot be changed(update, add, delete) after vdb is created
2. image of client proxy cannot be changed(update, add, delete) after vdb is created
3. if proxy is enabled, spec.proxy must be set and image must be non-empty.
4. if proxy is enabled, spec.subclusters[].proxy must be set, and replicas must be >= 0(at all times) and >= 1(for any new subcluster in the vdb)
5. check that the log level is one of these : TRACE|1=DEBUG|2=INFO|3=WARN|4=FATAL|5=NONE

[roypaulin]

Could you also add the following rules:

• if proxy is enabled, spec.proxy must be set and image must be non-empty.
• if proxy is enabled, spec.subclusters[].proxy must be set, and replicas must be >= 0(at all times) and >= 1(for any new subcluster in the vdb)

[roypaulin]

I made some api changes in my current PR. spec.proxy is now a pointer.