Add support for upstream textDocument/rename lsp support for terraform-ls

[teddylear]

A follow up to this issue on terraform-ls, wanted to make this here per @radeksimko suggestion to discuss design of implementing supporting functionality to this repo to be used by terraform-ls to perform renames on resoures/data sources/etc. This would hopefully help support an lsp rename operation on all hcl based configuration. I can start taking a look into this repo to see what functionality would have be added/missing, but very high level plan would be the following:

• Go to definition of an object
• Get all references of said object
• then perform rename operation on all references of object where relevant

If there's anything that should change in this approach or I'm missing please let me know. Also if possible would love to implement this.