Enhance ExternalIPPool validation #30961

Job	Run time
Check whether tests need to be run based on diff	14s
Verify docs and spelling	1m 1s
Build Antrea and antctl binaries	9m 48s
Golangci-lint (ubuntu-latest)	7m 43s
Go benchmark test	4m 33s
Golangci-lint (macos-latest)	12m 58s
Integration test	10m 16s
Unit test (ubuntu-latest)	6m 14s
Unit test (windows-2022)	15m 35s
Check tidy, code generation and manifest	5m 49s
Build Antrea Windows binaries	1m 48s
	1h 15m 59s

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