add option to enable extra toolchains, deprecated enable_rust #16

Job	Run time
Rust builds (using Delta extension) / Generate matrix	23s
Extension template / Generate matrix	22s
Extension template / Windows (windows_amd64, x64-windows-static-md)	18m 25s
Extension template / Linux (linux_amd64, ubuntu:18.04, x64-linux)	4m 0s
Extension template / Windows (windows_amd64_rtools, x64-mingw-static)	39m 55s
Extension template / MacOS (osx_amd64, x86_64, x64-osx)	5m 48s
Extension template / Linux (linux_amd64_gcc4, quay.io/pypa/manylinux2014_x86_64, x64-linux)	4m 19s
Extension template / MacOS (osx_arm64, arm64, arm64-osx)	5m 40s
Extension template / Linux (linux_arm64, ubuntu:18.04, arm64-linux)	4m 16s
Extension template / DuckDB-Wasm (wasm_mvp, wasm32-emscripten)	1m 53s
Extension template / DuckDB-Wasm (wasm_eh, wasm32-emscripten)	1m 59s
Extension template / DuckDB-Wasm (wasm_threads, wasm32-emscripten)	1m 43s
Rust builds (using Delta extension) / Linux (linux_amd64, ubuntu:18.04, x64-linux)	19m 37s
Rust builds (using Delta extension) / Linux (linux_amd64_gcc4, quay.io/pypa/manylinux2014_x86_64, x64-linux)	23m 55s
Rust builds (using Delta extension) / MacOS (osx_amd64, x86_64, x64-osx)	10m 42s
Rust builds (using Delta extension) / Linux (linux_arm64, ubuntu:18.04, arm64-linux)	18m 22s
Rust builds (using Delta extension) / MacOS (osx_arm64, arm64, arm64-osx)	10m 52s
Rust builds (using Delta extension) / Windows (windows_amd64, x64-windows-static-md)	40m 43s
Rust builds (using Delta extension) / DuckDB-Wasm	0s
	3h 32m 54s

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