Read terminal color codes in daemon client on every run

Currently terminal color codes are read once during daemon start-up, and then re-used on each run. So if the daemon is started in one environment (e.g. an IDE plugin) where colors are not available, and then run in another where they are available (e.g. a normal terminal), the colors stay disabled until the next daemon restart.

This is probably low priority because people don't often switch between running mypy daemon in a terminal and in IDE, and this doesn't cause mangled formatting.

まず、mypy daemon client が daemon の起動時にターミナルの色の使用可能性をどこで読み取り、各実行でその値をどこで再利用しているかを追跡します。daemon を再起動しなくても、IDE 環境と通常のターミナルを切り替える場合を含め、実行ごとに色の使用可能性が確認されれば完了です。