## Issue Addressed
Resolves#2602
## Proposed Changes
*Note: For a review it might help to look at the individual commits.*
### `boot_node`
Add support for the flags `dump-config` and `immediate-shutdown`. For `immediate-shutdown` the actual behavior could be described as `dump-config-and-exit`.
Both flags are handled in `boot_node::main`, which appears to be the simplest approach.
### `boot_node` regression tests
Added in `lighthouse/tests/boot_node.rs`.
### `CommandLineTestExec`
Factors out boilerplate related to CLI tests. It's used in the regression tests for `boot_node`, `beacon_node` and `validator_client`.
## Open TODO
Add tests for `boot_node` flags `enable-enr-auto-update` and `disable-packet-filter`. They end up in [`Discv5Config`](9ed2cba6bc/boot_node/src/config.rs (L29)), which doesn't support serde (de)serialization.
I haven't found a workaround - guidance would be appreciated.
## Issue Addressed
N/A
## Proposed Changes
Add unit tests for the various CLI flags associated with the beacon node and validator client. These changes require the addition of two new flags: `dump-config` and `immediate-shutdown`.
## Additional Info
Both `dump-config` and `immediate-shutdown` are marked as hidden since they should only be used in testing and other advanced use cases.
**Note:** This requires changing `main.rs` so that the flags can adjust the program behavior as necessary.
Co-authored-by: Paul Hauner <paul@paulhauner.com>
