refactor: Reflect upstream hcl-lang changes

[radeksimko]

Depends on hashicorp/hcl-lang#92

This is to prepare for module enhancements as described in hashicorp/vscode-terraform#715

Closes #658

One other minor side effect of the refactoring is that we now highlight the DefRange (if available) of a definition instead of the whole Range. For example, when you click to var.foobar it takes you to the same location, but variable "foobar" is highlighted, instead of the whole variable block.

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In addition to decoder changes described already in the upstream PR there is a few more changes here.

• This represents first steps towards getting rid of the context package which makes the codebase more prone to import cycles and goes against best practices. The remaining necessary context-related logic is broken down into the packages which produce the relevant data.
• Similarly passing dependencies via context goes against best practices in Go and reduces the chance of catching bugs early via compile-time checks
• This also represents first steps towards slimming down and getting rid of the ModuleManager

[jpogran]

After Radek walked me through the changes, and explained the refactoring, this looks like it will be a great change to make. I think this will not only help for modules, but also for the Prefill Required Fields CodeAction I want to implement later.

[radeksimko]

The CI failure is unrelated to the PR:

Error: Failed to query available provider packages

Could not retrieve the list of available versions for provider
thalesgroup/ciphertrust: no available releases match the given constraints

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