Extract Terraform extension (#10479)

This PR extracts Terraform support into an extension and removes the
built-in Terraform support from Zed.

Release Notes:

- Removed built-in support for Terraform, in favor of making it
available as
an extension. The Terraform extension will be suggested for download
when you
open a `.tf`, `.tfvars`, or `.hcl` file.

Cargo.lock

@@ -5463,7 +5463,6 @@ dependencies = [
  "tree-sitter-go",
  "tree-sitter-gomod",
  "tree-sitter-gowork",
- "tree-sitter-hcl",
  "tree-sitter-heex",
  "tree-sitter-jsdoc",
  "tree-sitter-json 0.20.0",
@@ -10417,15 +10416,6 @@ dependencies = [
  "tree-sitter",
 ]
 
-[[package]]
-name = "tree-sitter-hcl"
-version = "0.0.1"
-source = "git+https://github.com/MichaHoffmann/tree-sitter-hcl?rev=v1.1.0#636dbe70301ecbab8f353c8c78b3406fe4f185f5"
-dependencies = [
- "cc",
- "tree-sitter",
-]
-
 [[package]]
 name = "tree-sitter-heex"
 version = "0.0.1"
@@ -12683,6 +12673,13 @@ dependencies = [
  "zed_extension_api 0.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "zed_terraform"
+version = "0.0.1"
+dependencies = [
+ "zed_extension_api 0.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "zed_toml"
 version = "0.0.2"