Make references scope & type aware

[radeksimko]

Previously reference origins/addresses (such as var.foo) would be matched against addressable targets (attributes or blocks) in a strict fashion where addresses have to match exactly.

This patch makes origins scope & type aware as per hashicorp/hcl-lang#68 which in turn helps us "optimistically" recognize references to targets of unknown type.

Before

References to var.test are not recognized (no data provided on hover, reference not semantically highlighted, no go-to-definition etc.) due to the variable not having explicit type.

After

On hover we display the closest known target (for clarity).

[github-actions]

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