Refactor read pt. 2

[serathius]

continuation of #21573

Moving read code into subpackage.

/cc @ahrtr @fuweid

[codecov]

Codecov Report

❌ Patch coverage is 95.18072% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.45%. Comparing base (f0c0ca0) to head (a060bdd).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
server/etcdserver/read/read.go	96.00%	2 Missing ⚠️
server/etcdserver/server.go	80.00%	0 Missing and 1 partial ⚠️
server/etcdserver/v3_server.go	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
server/etcdserver/interface.go	100.00% <100.00%> (ø)
server/etcdserver/metrics.go	82.60% <ø> (+1.35%)	⬆️
server/etcdserver/raft.go	87.30% <100.00%> (+0.13%)	⬆️
server/etcdserver/read/metrics.go	100.00% <100.00%> (ø)
server/etcdserver/read/util.go	100.00% <100.00%> (ø)
server/etcdserver/util.go	100.00% <ø> (ø)
server/etcdserver/server.go	83.32% <80.00%> (+0.89%)	⬆️
server/etcdserver/v3_server.go	72.11% <66.66%> (ø)
server/etcdserver/read/read.go	89.20% <96.00%> (ø)

... and 17 files with indirect coverage changes

@@            Coverage Diff             @@
##             main   #21601      +/-   ##
==========================================
+ Coverage   68.37%   68.45%   +0.07%     
==========================================
  Files         429      432       +3     
  Lines       35391    35413      +22     
==========================================
+ Hits        24200    24243      +43     
+ Misses       9785     9771      -14     
+ Partials     1406     1399       -7     

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[serathius]

ping @ahrtr @fuweid

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahrtr, serathius

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[serathius]

/retest