nix: Return to building with crane (#21292)

This removes .envrc, putting it into gitignore as well as building with
crane, as it does not require an up to date hash for a FOD.

Release Notes:

- N/A

cc @mrnugget @jaredramirez

flake.lock

@@ -1,5 +1,20 @@
 {
   "nodes": {
+    "crane": {
+      "locked": {
+        "lastModified": 1732407143,
+        "narHash": "sha256-qJOGDT6PACoX+GbNH2PPx2ievlmtT1NVeTB80EkRLys=",
+        "owner": "ipetkov",
+        "repo": "crane",
+        "rev": "f2b4b472983817021d9ffb60838b2b36b9376b20",
+        "type": "github"
+      },
+      "original": {
+        "owner": "ipetkov",
+        "repo": "crane",
+        "type": "github"
+      }
+    },
     "flake-compat": {
       "locked": {
         "lastModified": 1696426674,
@@ -33,6 +48,7 @@
     },
     "root": {
       "inputs": {
+        "crane": "crane",
         "flake-compat": "flake-compat",
         "nixpkgs": "nixpkgs",
         "rust-overlay": "rust-overlay"