Rust

Make bon builders optional #1170

Job	Run time
build_lib_test (nightly)	51s
build_bin_spec (nightly)	1m 7s
build_lib_test (beta)	1m 15s
build_wasm (nightly)	45s
build_bin_spec (beta)	1m 7s
build_lib_test (stable)	1m 2s
build_wasm (beta)	51s
build_bin_spec (stable)	1m 0s
build_lib_test ($MSRV)	2m 27s
build_wasm (stable)	48s
build_bin_spec ($MSRV)	2m 19s
build_wasm ($MSRV)	1m 57s
clippy_format	1m 48s
lockfile	1m 8s
no_features_build_test (nightly)	28s
no_features_build_test (beta)	29s
no_features_build_test (stable)	18s
no_features_build_test ($MSRV)	34s
	20m 14s

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