## Issue Addressed
Closes#1823
## Proposed Changes
* Use OS-level file locking for validator keystores, eliminating problems with lockfiles lingering after ungraceful shutdowns (`SIGKILL`, power outage). I'm using the `fs2` crate because it's cross-platform (unlike `file-lock`), and it seems to have the most downloads on crates.io.
* Deprecate + disable `--delete-lockfiles` CLI param, it's no longer necessary
* Delete the `validator_dir::Manager`, as it was mostly dead code and was only used in the `validator list` command, which has been rewritten to read the validator definitions YAML instead.
## Additional Info
Tested on:
- [x] Linux
- [x] macOS
- [x] Docker Linux
- [x] Docker macOS
- [ ] Windows
## Issue Addressed
Resolve#1652
## Proposed Changes
Adds a cli option for voluntary exits. The flow is similar to prysm's where after entering the password for the validator keystore (or load password from `secrets` if present) the user is given multiple warnings about the operation being irreversible, then redirected to the docs webpage(not added yet) which explains what a voluntary exit is and the consequences of exiting and then prompted to enter a phrase from the docs webpage as a final confirmation.
Example usage
```
$ lighthouse --testnet zinken account validator exit --validator <validator-pubkey> --beacon-node http://localhost:5052
Running account manager for zinken testnet
validator-dir path: "..."
Enter the keystore password: for validator in ...
Password is correct
Publishing a voluntary exit for validator: ...
WARNING: This is an irreversible operation
WARNING: Withdrawing staked eth will not be possible until Eth1/Eth2 merge Please visit [website] to make sure you understand the implications of a voluntary exit.
Enter the phrase from the above URL to confirm the voluntary exit:
Exit my validator
Published voluntary exit for validator ...
```
## Additional info
Not sure if we should have batch exits (`--validator all`) option for exiting all the validators in the `validators` directory. I'm slightly leaning towards having only single exits but don't have a strong preference.
## Issue Addressed
NA
## Proposed Changes
- Refactor the `bls` crate to support multiple BLS "backends" (e.g., milagro, blst, etc).
- Removes some duplicate, unused code in `common/rest_types/src/validator.rs`.
- Removes the old "upgrade legacy keypairs" functionality (these were unencrypted keys that haven't been supported for a few testnets, no one should be using them anymore).
## Additional Info
Most of the files changed are just inconsequential changes to function names.
## TODO
- [x] Optimization levels
- [x] Infinity point: https://github.com/supranational/blst/issues/11
- [x] Ensure milagro *and* blst are tested via CI
- [x] What to do with unsafe code?
- [x] Test infinity point in signature sets
