Remove the use of Cargo `path` ref for the `bdk_chain` and `bdk_file_store` dependencies. This is the first step to move `bdk_wallet` into a new workspace.
Also fixed CI failures as we were testing no-std without hashbrown.
### Checklists
#### All Submissions:
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* [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
* [x] I ran `cargo fmt` and `cargo clippy` before committing