refactor(timer): use polymorphism to eliminate conditions

[hwjiangkai]

What problem does this PR solve?

optimize code logic to improve performance

Issue Number: close #236

Problem Summary

What is changed and how does it work?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

[codecov]

Codecov Report

Merging #264 (23018e3) into main (ca600ab) will increase coverage by 0.58%.
The diff coverage is 84.69%.

❗ Current head 23018e3 differs from pull request most recent head 1bb2361. Consider uploading reports for the commit 1bb2361 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #264      +/-   ##
==========================================
+ Coverage   64.00%   64.58%   +0.58%     
==========================================
  Files         129      129              
  Lines       11575    11676     +101     
==========================================
+ Hits         7408     7541     +133     
+ Misses       3643     3611      -32     
  Partials      524      524              

Impacted Files	Coverage Δ
...al/controller/trigger/subscription/subscription.go	64.58% <0.00%> (-4.31%)	⬇️
internal/trigger/reader/reader.go	66.66% <66.66%> (+1.96%)	⬆️
internal/trigger/trigger/trigger.go	79.03% <72.00%> (-0.58%)	⬇️
internal/controller/trigger/controller.go	39.54% <72.72%> (+0.88%)	⬆️
internal/timer/timingwheel/timingwheel.go	89.32% <90.47%> (+9.63%)	⬆️
internal/controller/trigger/worker/worker.go	83.11% <100.00%> (-0.15%)	⬇️
internal/gateway/gateway.go	69.60% <100.00%> (-0.30%)	⬇️
internal/timer/timingwheel/bucket.go	100.00% <100.00%> (+0.97%)	⬆️
internal/trigger/transform/transformer.go	100.00% <100.00%> (+6.12%)	⬆️
... and 3 more

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[ifplusor]

LGTM