Enable for_each, count, self.* and dynamic support

[dbanck]

This PR pulls in all the upstream changes to hcl-lang and terraform-schema.

With the changes, we introduce:

• Support for self.* references: Introduce support for self.* references hcl-lang#163
• dynamic block support, including label and content completion: Enable dynamic label completions hcl-lang#154
• Support for each.* references: Use local ref. targets for each.* references hcl-lang#162
• Support for count.index references Use local ref. targets for count.index hcl-lang#160

Closes #1096
Closes #859
Closes #1095
Closes #1093
Closes #530

[radeksimko]

LGTM

[github-actions]

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