Optimize getting routes function for Windows #28381

Job	Run time
Verify docs and spelling	34s
Check whether tests need to be run based on diff	22s
Unit test (windows-2022)	24m 8s
Unit test (ubuntu-latest)	11m 34s
Go benchmark test	8m 36s
Golangci-lint (macos-latest)	9m 4s
Build Antrea and antctl binaries	19m 1s
Golangci-lint (ubuntu-latest)	14m 49s
Integration test	13m 47s
Check tidy, code generation and manifest	9m 28s
Build Antrea Windows binaries	2m 47s
	1h 54m 10s

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