[PFS-230] Initial fileset service protos

[brycemcanally]

This PR contains the initial protos for the new fileset service described here: https://www.notion.so/2024-02-09-Filesets-gRPC-Service-10f40b1eec9a4af8b48100aadb710fc9

[jrockway]

Protos look fine.

While I don't think there is any specific rule here, this is the first proto file not named the same as the directory it's in; i.e. normally this would be storage.proto.

I think you need to do two more things here:

1. Run Gazelle to generate the go build rules for this new package (bazel run //:gazelle).

2. Export protos from this package so the builder can see them by adding this rule to the newly-generated src/storage/BUILD.bazel file:

filegroup(
    name = "protos",
    srcs = glob(["*.proto"]),
    visibility = ["//src:__pkg__"],
)

3. Add this new filegroup to src/BUILD.bazel's all_protos filegroup.

(Basically if there is no BUILD file in the directory, we can glob the *.protos for make_proto... but after you run Gazelle so you can use the generated code from Go, then the glob won't work anymore and you have to explicitly select the protos.)

[jrockway]

Also need "bazel run //:buildifier"; the list of deps for the all_protos target should be sorted and that tool will do it for you.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.21%. Comparing base (9245e70) to head (14ce5ed).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9893      +/-   ##
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- Coverage   58.31%   58.21%   -0.10%     
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  Files         605      605              
  Lines       73341    73341              
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- Hits        42766    42696      -70     
- Misses      30018    30090      +72     
+ Partials      557      555       -2     

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[bbonenfant]

LGTM, however, I'd like to know if this is intended to be customer facing/available through the SDK. Although these changes always generate protos, if they are within a new grpc service then the INT teams needs to manually expose these within the client. So if/when these are intended to be user-facing let us know and we'll expose them