refactor: recreate with kubebuilder go/v4 plugin

[nakamasato]

what

Migration from go/v3 to go/v4

why

To make the code dependencies up-to-date

Ref

https://book.kubebuilder.io/plugins/go-v4-plugin

[codecov]

Codecov Report

Merging #260 (beca658) into main (3594bd9) will decrease coverage by 0.75%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #260      +/-   ##
==========================================
- Coverage   62.18%   61.43%   -0.75%     
==========================================
  Files           6        6              
  Lines         669      669              
==========================================
- Hits          416      411       -5     
- Misses        203      207       +4     
- Partials       50       51       +1     

Files Changed	Coverage Δ
internal/controller/mysql_controller.go	54.34% <ø> (-2.72%)	⬇️
internal/controller/mysqldb_controller.go	36.88% <ø> (ø)
internal/controller/mysqluser_controller.go	69.03% <ø> (ø)