Allow to configure the default enabled state of mirrord

[danielwinkler]

Right now the extension is disabled by default, so whenever you restart VS code it will not remember the last state.
One workaround is to make use of "support MIRRORD_ACTIVE=1 config to enforce mirrord usage even if toggle is off", but the downside is that it will not be reflected in the UI.

It would be great to have the options in the settings, that will define the default state, but still allow to disable it by the user using the UI.