Rust

Launch watchers once per operator process #356

Job	Run time
Tests (release), stable toolchain	7m 0s
Tests, unstable toolchain (beta)	4m 47s
Tests, stable toolchain	4m 44s
Tests, unstable toolchain (nightly)	4m 51s
Tests (release), minimum supported toolchain	9m 27s
	30m 49s

Provide feedback