plannable import: support step.ConfigExact = [true|false] for all config sources

[bbasata]

This PR extends ImportState auto-generated import blocks to work with step.ConfigFile and step.ConfigDirectory. It adds a step.ConfigExact flag to opt out.

cc: @gdavison

[bbasata]

cc: @austinvalle, I'd like to get your input on how this feels directionally, so we can decide whether to ship it in a release candidate.

[austinvalle]

TLDR, big fan of the approach/feedback if it works well for provider developers and think we should expand on it 👍🏻

[bbasata]

TLDR, big fan of the approach/feedback if it works well for provider developers and think we should expand on it 👍🏻

I re-discovered #383 just now.

[gdavison]

Yes, #383 will be very useful for us. In the string-based Config flow, we append, sometimes several levels deep, common configuration. Being able to add files or merge directories would simplify the use of ConfigDirecotory

[austinvalle]

I have no major qualms with the approach, just a thought on naming

[austinvalle]

LGTM 🚀