Periodically pause copying ledger nodes during online_delete #4166

Job	Run time
dependencies (linux, gcc, Debug)	3m 14s
dependencies (linux, gcc, Release)	2m 15s
dependencies (linux, clang, Debug)	2m 46s
dependencies (linux, clang, Release)	2m 18s
conan	2m 48s
test (linux, gcc, Debug)	11m 11s
coverage (linux, gcc, Debug)	13m 13s
test (linux, gcc, Debug, -Dunity=ON)	7m 53s
test (linux, gcc, Release)	12m 1s
test (linux, gcc, Release, -Dunity=ON)	8m 3s
test (linux, clang, Debug)	9m 7s
test (linux, clang, Debug, -Dunity=ON)	6m 17s
test (linux, clang, Release)	11m 12s
test (linux, clang, Release, -Dunity=ON)	8m 18s
	1h 40m 36s

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