[2.2][Security] Outsource all the BCrypt heavy lifting to a library

| Q             | A
| ------------- | ---
| Bug fix?      | [no]
| New feature?  | [no]
| BC breaks?    | [no]
| Deprecations? | [no]
| Tests pass?   | [yes]
| License       | MIT

The [BCrypt bundle](https://github.com/elnur/ElnurBlowfishPasswordEncoderBundle) is already using the library.