WIP: Set CRATES mechanically

Use shell to set the `CRATES` env var used by `run_task.sh`.

This patch needs a PR to merge into maintainer tools before it can be
used, we then need to set the commit hash in
`.github/workflows/rust.yml`.

rust-bitcoin/rust-bitcoin-maintainer-tools#11

contrib/crates.sh

@@ -1,8 +1,9 @@
+# Sourced by `rust-bitcoin-maintainer-tools/ci/run_task.sh`.
+#
 # No shebang, this file should not be executed.
 # shellcheck disable=SC2148
 #
 # disable verify unused vars, despite the fact that they are used when sourced
 # shellcheck disable=SC2034
 
-# Crates in this workspace to test (note "fuzz" is only built not tested).
-CRATES=("addresses" "base58" "bitcoin" "hashes" "internals" "io" "units" "fuzz")
+CRATES="$(cargo metadata --no-deps --format-version 1 | jq -j -r '.packages | map(.manifest_path | rtrimstr("/Cargo.toml") | ltrimstr("'"$PWD"'/")) | join(" ")')"