feat(nvidia/hw-slowdown): use common db pkg for events

[gyuho]

c.f., #336

Requires #341.

Tested

[xiang90]

need to improve the test coverage to pass CI

[codecov]

Codecov Report

Attention: Patch coverage is 50.70423% with 35 lines in your changes missing coverage. Please review.

Project coverage is 22.56%. Comparing base (5d1d369) to head (efab191).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
components/accelerator/nvidia/query/nvml/nvml.go	0.00%	15 Missing ⚠️
...nents/accelerator/nvidia/query/nvidia_smi_query.go	52.00%	12 Missing ⚠️
components/accelerator/nvidia/query/query.go	0.00%	6 Missing ⚠️
...onents/accelerator/nvidia/hw-slowdown/component.go	80.00%	1 Missing ⚠️
internal/server/server.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #342      +/-   ##
==========================================
- Coverage   22.72%   22.56%   -0.16%     
==========================================
  Files         291      289       -2     
  Lines       26161    25869     -292     
==========================================
- Hits         5944     5838     -106     
+ Misses      19605    19430     -175     
+ Partials      612      601      -11     

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