Support for packer hcl files

[sanga]

Currently *.hcl is detected as terraform. Packer files are however *.pkr.hcl (or *.pkr.json). So currently they are incorrectly detected as terraform when they should be detected as packer. So they have the terraform grammar and terraform lsp applied, both of which give spurious errors. See https://developer.hashicorp.com/packer/docs/templates/hcl_templates#builds

[sanga]

I have this solved locally via an LLM produced solution (which is pretty minimal) and can PR if people are amenable to such changes