mirror:support one mirror process to back up specified buckets #4780

Job	Run time
vetchecks	1m 57s
Test on Go 1.22.x and ubuntu-latest	9m 25s
Test on Go 1.22.x and macos-latest	1m 35s
Test on Go 1.22.x and windows-latest	3m 36s
	16m 33s

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