Split Msf::HostState into own file

MSP-11124
Fix indent in Msf::HostState

MSP-11124
Fix comment style in Msf::HostState

MSP-11124
Extract Msf::ServiceState

MSP-11124

Extract Msf::ServiceState from `lib/msf/core/db.rb` and put it into
`lib/msf/core/service_state.rb`.
Fix indentation in Msf::ServiceState

MSP-11124
Fix code style in Msf::ServiceState

MSP-11124
Extract Msf::DatabaseEvent

MSP-11124

Extract `Msf::DatabaseEvent` from `lib/msf/core/db.rb` into a more
conventional `lib/msf/core/database_event.rb`.
Fix indentation and whitespace in Msf::DatabaseEvent

MSP-11124
Fix code style

MSP-11124

Fix comment style and order methods.
Extract Msf::DBImportError

MSP-11124
Merge db.rb into db_manager.rb

MSP-11124

The class name is DBManager, so the correct file name is db_manager.rb
Extract Msf::DBManager::Sink

MSP-11124

Extract attributes and methods associated with the deprecated sink.
Extract Msf::DBManagerSink examples to shared example

MSP-11124
Move Msf::DBManager#sync to Msf::DBManager::Sink

MSP-11124

The comment on `#sync` says it's related to `sink`, so move it into its
Module.
Extract Msf::DBManager::Workspace

MSP-11124

Gather together all workspace related methods into
`Msf::DBManager::Workspace` and include it in `Msf::DBManager`.
Extract Msf::DBManager::Workspace examples to shared example

MSP-11124
Extract Msf::DBManager::ModuleCache

MSP-11124

Extract methods related to the module cache state and maintenance to
`Msf::DBManager::ModuleCache`.
Extract Msf::DBManager::ModuleCache shared examples

MSP-11124
Move #match_values to Msf::DBManager::ModuleCache

MSP-11124

`#match_values` is only used in `#search_modules`, so `#match_values`
should be grouped with `#search_modules` in
`Msf::DBManager::ModuleCache`.
Test for #match_values

MSP-11124