*: namespace quota

[vivekpatani]

To add functionality surroundind the namespace quotas.
Ability to set, delete, list, and get quotas.
Framework to interact with core etcd ops.

This PR is against master, a related PR against branch-3.4 is made here: #13486

Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.

[vivekpatani]

@wenjiaswe @ptabor @serathius @wojtek-t @hexfusion @jingyih

3.4 - https://github.com/etcd-io/etcd/pull/13486/files (we had initially started developing on 3.4)

Technical document: https://docs.google.com/document/d/1POdNdFBgpcGqLwurZjy8qQki6beOoVIcElTqHy4DnnA/edit
etcd GitHub issue: #10084
k8s: kubernetes/kubernetes#102078
k8s KEP: kubernetes/enhancements#2754
Slide Deck: https://drive.google.com/file/d/1wmssxH0fpRwRKmL7TCW5S_LPzjkiLrHJ/view

[JmPotato]

Thx for your work! But I'm wondering that this big change is hard to review, so any splitting would be helpful 😢.

[vivekpatani]

@JmPotato Hi sure, let me logically chunk them out, thank you. I will update you once I break them apart.

[codecov-commenter]

Codecov Report

Merging #13516 (1643634) into main (1597219) will decrease coverage by 1.09%.
The diff coverage is 68.39%.

❗ Current head 1643634 differs from pull request most recent head bb39cec. Consider uploading reports for the commit bb39cec to get more accurate results

@@            Coverage Diff             @@
##             main   #13516      +/-   ##
==========================================
- Coverage   75.11%   74.01%   -1.10%     
==========================================
  Files         448      458      +10     
  Lines       37181    37909     +728     
==========================================
+ Hits        27929    28059     +130     
- Misses       7484     8022     +538     
- Partials     1768     1828      +60     

Flag	Coverage Δ
all	74.01% <68.39%> (-1.10%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
api/v3rpc/rpctypes/error.go	90.47% <ø> (ø)
etcdctl/ctlv3/command/printer.go	22.48% <0.00%> (-0.72%)	⬇️
etcdctl/ctlv3/command/printer_simple.go	57.55% <0.00%> (-3.56%)	⬇️
server/config/config.go	79.76% <ø> (ø)
server/etcdserver/api/v3rpc/util.go	74.19% <ø> (ø)
server/storage/mvcc/kv.go	40.00% <ø> (ø)
server/storage/schema/bucket.go	88.88% <ø> (ø)
client/v3/namespacequota.go	15.25% <15.25%> (ø)
...grpcproxy/adapter/namespacequota_client_adapter.go	20.00% <20.00%> (ø)
client/v3/retry.go	71.65% <27.27%> (-4.21%)	⬇️
... and 74 more

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[vivekpatani]

@JmPotato @wenjiaswe @ptabor @serathius @wojtek-t @hexfusion @jingyih rebased the PR, bumping again. Sorry it took so long.

I've tried to breakdown the PR into more logical components so that it builds up in the following fashion:

1. Added/Generated most of the proto files needed for this feature.
2. NamespaceQuotaEnforcement controls if the quota needs to be in soft, hard, or disabled mode.
3. Add metrics required to understand how quotas are being used and affect etcd, added go.mod changes, and creating an index required to CRUD quotas.
4. Add necessary functions to recover quotas when a member/cluster starts/restarts/join
5. Add the central part of the quota, the namespace quota manager. This has most of functionality of quotas.
6. Add relevant errors that may occur when dealing with quotas.
7. Server changes to accommodate quota operations, and subsequent raft changes.
8. Testing
9. Client side changes to accommodate quotas.
10. Minor fixes
11. gRPC proxy changes

Please feel free to reach out with any questions, feedback is welcome. Thank you.

[vivekpatani]

As discussed in meeting on June 2, 2022, this will be reviewed at a later time, potentially 3.7.x/3.8.x.