Add Migration Support (#11)

* Add migration support

* Add SemVersion serialization and migration handling

Introduce SemVersionSerializer for BSON serialization. Update MongoVaultMigrationManager for improved version comparison and migration handling, including up and down operations.

* Refactor configuration handling in Vault classes

Changed visibility of Migration properties to internal and refactored VaultConfigurationManager to use MongoVaultOptions directly. This improves encapsulation and aligns property management more consistently across classes.