Handle self = false, add warning about compact and sort

[Nuru]

what

• Handle self = false
• Add warning about compact and sort

why

• Setting self = false in a rule (meaning the rule does not apply to the security group it is being associated with) was causing an empty rule to be created and/or causing conflicts with other rule elements. Now it works like self = null works.
• Explain some causes of the dreaded "Invalid for_each argument" error and what to do to fix it.

references

• Sort should retain length of list hashicorp/terraform#31035
• Unknown values should not block successful planning hashicorp/terraform#30937 (comment)

[Nuru]

/test all