feat: use .rustfmt.toml for formatting options

We previously did this with the `cargo fmt-stacks` command because these
config options were not supported in .rustfmt.toml, but they are now
supported by the nightly build. Using this directly is better than the
alias because we do not need to remember to run the alias.

Author: obycode

.cargo/config.toml

@@ -1,6 +1,5 @@
 [alias]
 stacks-node = "run --package stacks-node --"
-fmt-stacks = "fmt -- --config group_imports=StdExternalCrate,imports_granularity=Module"
 clippy-stacks = "clippy -p libstackerdb -p stacks-signer -p pox-locking -p clarity -p libsigner -p stacks-common --no-deps --tests --all-features -- -D warnings"
 
 # Uncomment to improve performance slightly, at the cost of portability

.rustfmt.toml

@@ -0,0 +1,2 @@
+group_imports = "StdExternalCrate"
+imports_granularity = "Module"

.vscode/settings.json

@@ -1,7 +1,11 @@
 {
-    "lldb.adapterType": "native",
-    "lldb.launch.sourceLanguages": ["rust"],
+    "lldb.launch.sourceLanguages": [
+        "rust"
+    ],
     "rust-analyzer.runnables.extraEnv": {
         "BITCOIND_TEST": "1"
-    }
+    },
+    "rust-analyzer.rustfmt.extraArgs": [
+        "+nightly"
+    ]
 }