Update semantic token block label type

[dbanck]

This PR updates the type for block labels from string to enum member.

It's the first step in providing more contextual information on block labels. With a schema update, it will be possible to differentiate between multiple block labels. This will allow us to report two different tokens for block labels where the first one stays enum member and the second one becomes a string.

We've tried different token types, like class, macro, method, and enumMember and settled on the latter. enumMember makes the most sense from a semantic perspective and has good highlighting in the default themes.

Having semantic tokens for block labels enables better highlighting for nested blocks.

Before (no LS)

After (with LS)

For a smoother user experience, we propose to update the static grammar for block labels from entity.name.tag.terraform to variable.other.enummember. This change would update the raw grammar version (no LS) to this:

Closes #777

[radeksimko]

LGTM

[jpogran]

Depending on your theme, the 'no LS' does highlight differently than strings.

Dark+ (default):

Light+:

I do agree on aligning the scopes between the textmate grammar and the semantic token, just pointing out it does do something :)

[github-actions]

This functionality has been released in v0.26.0 of the language server.
If you use the official Terraform VS Code extension, it will prompt you to upgrade to this version automatically upon next launch or within the next 24 hours.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

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