Update initializationOptions per recent LS changes

[radeksimko]

This is to reflect last changes from the following PRs in the extension settings:

• settings: repurpose indexer-related options terraform-ls#1003
• settings: break down indexing options terraform-ls#1010
• settings: break down terraform CLI related settings terraform-ls#1011

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The user-facing changes here are:

1. Updated deprecation message to rootModulePaths to reflect that this option is going away for good and nudge users to add folders to the workspace instead.
2. New indexing config subsection for indexer-related options.

terraform options are already aligned with LS, so that's just internal change.

[jpogran]

💯

[github-actions]

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