log: change log level to reduce the noise logs

[chlins]

1. Change some logs level to reduce the noise.
2. Wrap the go-redis.Nil error as ErrNotFound to avoid confusing

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Comprehensive Summary of your change

Issue being fixed

Fixes #(issue)

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• Well Written Title and Summary of the PR
• Label the PR as needed. "release-note/ignore-for-release, release-note/new-feature, release-note/update, release-note/enhancement, release-note/community, release-note/breaking-change, release-note/docs, release-note/infra, release-note/deprecation"
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• Made sure tests are passing and test coverage is added if needed.
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[codecov]

Codecov Report

Merging #19165 (7c0013f) into release-2.9.0 (fbdc03b) will decrease coverage by 0.03%.
The diff coverage is 57.14%.

@@                Coverage Diff                @@
##           release-2.9.0   #19165      +/-   ##
=================================================
- Coverage          67.42%   67.39%   -0.03%     
=================================================
  Files                993      993              
  Lines             108864   108866       +2     
  Branches            2751     2751              
=================================================
- Hits               73397    73372      -25     
- Misses             31518    31547      +29     
+ Partials            3949     3947       -2     

Flag	Coverage Δ
unittests	67.39% <57.14%> (-0.03%)	⬇️

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

Files Changed	Coverage Δ
src/core/session/session.go	34.82% <0.00%> (ø)
src/server/registry/manifest.go	66.90% <0.00%> (ø)
src/lib/cache/redis/redis.go	71.30% <100.00%> (-0.38%)	⬇️
src/pkg/notifier/notifier.go	82.35% <100.00%> (ø)

... and 9 files with indirect coverage changes

[wy65701436]

lgtm