chore(ci): upload coverage tarball for CI runs

Just realized that this is fairly easy to do, and this might be helpful
for us in figuring out where we could improve test coverage.

Author: addaleax

.evergreen.yml

@@ -146,6 +146,16 @@ functions:
           export NODE_JS_VERSION=${node_js_version}
           source .evergreen/.setup_env
           npm run test-ci
+          tar cvzf coverage.tgz coverage
+    - command: s3.put
+      params:
+        aws_key: ${aws_key}
+        aws_secret: ${aws_secret}
+        local_file: src/coverage.tgz
+        remote_file: mongosh/binaries/${revision}/${revision_order_id}/coverage-${build_variant}.tgz
+        bucket: mciuploads
+        permissions: public-read
+        content_type: application/x-gzip
   test_vscode:
     - command: shell.exec
       params: