Introduce support for self.* references

[radeksimko]

Architecture Background

One vs Two schema flags (targets vs origins)

Originally the hope/plan was to have just a single "flag" in the schema under the Extensions - SelfRef: true, just like we have for Count and ForEach and will have for dynamic blocks. However, it turns out that isn't most practical. This is because we collect reference targets with the appropriate addresses separately from origins and because we would have to traverse through the rest of a potentially deeply nested and long block, to find out whether a particular target needs a local self address or not.

So we instead introduce the additional DependentBodySelfRef: true which implies that any attributes and blocks within the body will be collected as a target with an additional self.* local address. This will then be enabled for Terraform within the resource and data blocks and allows us to do the target collection without knowing whether that address is needed or not in the rest of the block.

Contextual Address

Since reference targets can now have both local (LocalAddr) and "absolute" (Addr) address, this needs to be considered when rendering the address in completion, hover and elsewhere. In Terraform, self.* addresses are relevant under provisioner, connection and some other blocks, and the assumption is that these refer to the outermost block/body, i.e. resource block.

UX Impact

Completion

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