Merge pull request #731 from MaterializeInc/clonable-threaded-producer #669

Job	Run time
check-minimal-versions	1m 7s
check (macos-11.0)	1s
lint	2m 17s
test (7.7.0, 3.7)	2m 30s
check (windows-2019, cmake-build,libz-static,curl-static, cmake-build,libz-static,curl-static)	4m 30s
test (7.5.1, 3.6)	2m 24s
check (ubuntu-20.04, tracing)	1m 58s
test (7.5.1, 3.5)	2m 34s
check (ubuntu-20.04, cmake-build,ssl-vendored,gssapi-vendored,libz-static,curl-static,zstd, cmake...	3m 24s
	20m 45s

Provide feedback