src: generate rust code for more aggregation functions

[spongedu]

Update rust proto files for support more aggregation functions. See #65 for proto/go modifications

[coocood]

LGTM

[breezewish]

Where is the change of the protobuf file?

[coocood]

@breeswish
#65

[breezewish]

@coocood Thanks! I found something wired. I looked at the PR your referenced, and found out that it contains changes that reverted my another PR for generated files. See #66. Are there anything that I missed?

[coocood]

@breeswish @spongedu
Well, there is a conflict between the two PRs.
I think we can close this one.

[breezewish]

@coocood I think we need to set a repeatable environment so that every one will generate exactly the same file for the same protobuf source file. According to PR #66 and PR #65 it seems that current setup instructions in README cannot provide such guarantees.