feat: optimize performance of service-import-controller

[codecov[bot]]

Codecov Report

Attention: 63 lines in your changes are missing coverage. Please review.

Comparison is base (72024ac) 33.03% compared to head (e9e59c4) 33.03%.

Files	Patch %	Lines
pkg/controllers/mcs/service_import_controller.go	0.00%	62 Missing :warning:
pkg/controllers/follower/controller.go	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #313 +/- ## ========================================== - Coverage 33.03% 33.03% -0.01% ========================================== Files 152 152 Lines 17592 17595 +3 ========================================== Hits 5812 5812 - Misses 11292 11295 +3 Partials 488 488 ``` | [Flag](https://app.codecov.io/gh/kubewharf/kubeadmiral/pull/313/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=kubewharf) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/kubewharf/kubeadmiral/pull/313/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=kubewharf) | `33.03% <1.56%> (-0.01%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=kubewharf#carryforward-flags-in-the-pull-request-comment) to find out more.

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