feat: introduce runkv client

[MrCroxx]

Introduce RunkvClient. Which fetch router from rudder and decide target wheel to send requests automatically.

Changes:

• Introduce RunkvClient. Which fetch router from rudder and decide target wheel to send requests automatically.
• Wheel return Redirect error if KvRequest target is not in itself. TODO: Return Redirect when target is not legal raft leader.
• Refactor kv.proto.

TODOs:

• Return Redirect when target is not legal raft leader.
• Restore integration tests with runkv client.

[codecov[bot]]

Codecov Report

Merging #156 (49dbc63) into main (3b5c7fc) will decrease coverage by 1.77%. The diff coverage is 1.88%.

@@            Coverage Diff             @@
##             main     #156      +/-   ##
==========================================
- Coverage   54.98%   53.21%   -1.78%     
==========================================
  Files          80       84       +4     
  Lines        7973     8246     +273     
==========================================
+ Hits         4384     4388       +4     
- Misses       3589     3858     +269     

Impacted Files	Coverage Δ
client/src/client.rs	0.00% <0.00%> (ø)
client/src/error.rs	0.00% <0.00%> (ø)
client/src/worker/heartbeater.rs	0.00% <0.00%> (ø)
proto/src/lib.rs	2.70% <0.00%> (-11.59%)	:arrow_down:
rudder/src/meta/mem.rs	0.00% <0.00%> (ø)
rudder/src/meta/mod.rs	0.00% <ø> (ø)
rudder/src/service.rs	0.00% <0.00%> (ø)
wheel/src/components/command.rs	0.00% <ø> (ø)
wheel/src/components/fsm.rs	7.58% <0.00%> (-0.71%)	:arrow_down:
wheel/src/components/raft_manager.rs	0.00% <0.00%> (ø)
... and 10 more

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