* configs/configschema: extend block.AttributeByPath to descend into Objects
This commit adds a recursive Object.AttributeByPath function which will step through Attributes with NestedTypes. If an Attribute without a NestedType is encountered while there is still more to the path, it will return nil.
* configs/configschema: fix missing "computed" attributes from NestedObject's ImpliedType
listOptionalAttrsFromObject was not including "computed" attributes in the list of optional object attributes. This is now fixed. I've also added some tests and fixed some panics and otherwise bad behavior when bad input is given. One natable change is in ImpliedType, which was panicking on an invalid nesting mode. The comment expressly states that it will return a result even when the schema is inconsistent, so I removed the panic and instead return an empty object.
This is part of a general effort to move all of Terraform's non-library
package surface under internal in order to reinforce that these are for
internal use within Terraform only.
If you were previously importing packages under this prefix into an
external codebase, you could pin to an earlier release tag as an interim
solution until you've make a plan to achieve the same functionality some
other way.