ENT-12414: Use `librsync`'s Stream API in `GET <FILENAME>` requests #1642

Job	Run time
shellcheck_tests / Run shellcheck on shell scripts	40s
unit_tests / Run Unit Tests	48s
macos_unit_tests	0s
acceptance_tests	0s
valgrind_tests	0s
windows_acceptance_tests	0s
static_check	0s
asan_unit_tests	0s
valgrind_check	0s
	1m 28s

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