Test distributed registration

[hanahmily]

Integration test for distributed registration:

1. Liaison node could register to the etcd
2. Data node could register to the etcd

Besides the registration, I also prepend a "namespace" to keys in etcd. With this setting, we could deploy several banyandb clusters in a etcd cluster.

[codecov-commenter]

Codecov Report

Merging #329 (dbc70c8) into main (b034d20) will increase coverage by 0.19%.
The diff coverage is 92.00%.

@@            Coverage Diff             @@
##             main     #329      +/-   ##
==========================================
+ Coverage   40.42%   40.61%   +0.19%     
==========================================
  Files         110      110              
  Lines       11710    11726      +16     
==========================================
+ Hits         4734     4763      +29     
+ Misses       6505     6494      -11     
+ Partials      471      469       -2     

Files Changed	Coverage Δ
banyand/measure/metadata.go	66.42% <0.00%> (ø)
banyand/metadata/schema/property.go	0.00% <0.00%> (ø)
banyand/stream/metadata.go	68.10% <0.00%> (ø)
banyand/metadata/client.go	40.93% <100.00%> (+1.62%)	⬆️
banyand/metadata/schema/etcd.go	50.37% <100.00%> (+3.36%)	⬆️
banyand/metadata/schema/group.go	59.64% <100.00%> (+1.58%)	⬆️
banyand/metadata/schema/node.go	7.69% <100.00%> (ø)
banyand/metadata/schema/watcher.go	71.59% <100.00%> (ø)

... and 3 files with indirect coverage changes

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