Add CPU architecture to the remote extensions object key (#11590)

ARM computes are incoming and we need to account for that in remote
extensions. Previously, we just blindly assumed that all computes were
x86_64.

Note that we use the Go architecture naming convention instead of the
Rust one directly to do our best and be consistent across the stack.

Part-of: https://github.com/neondatabase/cloud/issues/23148

Signed-off-by: Tristan Partin <tristan@neon.tech>

test_runner/regress/test_download_extensions.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import os
+import platform
 import shutil
 import tarfile
 from typing import TYPE_CHECKING
@@ -58,7 +59,18 @@ def test_remote_extensions(
     extensions_endpoint = f"http://{host}:{port}/pg-ext-s3-gateway"
 
     build_tag = os.environ.get("BUILD_TAG", "latest")
-    archive_route = f"{build_tag}/v{pg_version}/extensions/test_extension.tar.zst"
+
+    # We have decided to use the Go naming convention due to Kubernetes.
+    arch = platform.machine()
+    match arch:
+        case "aarch64":
+            arch = "arm64"
+        case "x86_64":
+            arch = "amd64"
+        case _:
+            pass
+
+    archive_route = f"{build_tag}/{arch}/v{pg_version}/extensions/test_extension.tar.zst"
     tarball = test_output_dir / "test_extension.tar"
     extension_dir = (
         base_dir / "test_runner" / "regress" / "data" / "test_remote_extensions" / "test_extension"