fix: cache key stability (#142)

Ensure consistency of main and post configuration by storing and
restoring it from state, which in turn ensures cache key stability.

Also:
* Fixed some typos.
* Use core.error for logging errors.
* Fix inverted condition on cache-all-crates.

Reverts: #138
Fixes #140

README.md

@@ -101,7 +101,6 @@ This cache is automatically keyed by:
 - the value of some compiler-specific environment variables (eg. RUSTFLAGS, etc), and
 - a hash of all `Cargo.lock` / `Cargo.toml` files found anywhere in the repository (if present).
 - a hash of all `rust-toolchain` / `rust-toolchain.toml` files in the root of the repository (if present).
-- a hash of installed packages as generated by `cargo install --list`.
 
 An additional input `key` can be provided if the builtin keys are not sufficient.
 
@@ -137,7 +136,7 @@ otherwise corrupt the cache on macOS builds.
 This specialized cache action is built on top of the upstream cache action
 maintained by GitHub. The same restrictions and limits apply, which are
 documented here:
-https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows
+[Caching dependencies to speed up workflows](https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows)
 
 In particular, caches are currently limited to 10 GB in total and exceeding that
 limit will cause eviction of older caches.