chore(ci): migrate codecov upload to codecov-cli v11.2.8 [SRE-1580]

[raj-vangari]

Summary

• Removes codecov/codecov orb from the orbs: section
• Replaces codecov/upload step with direct codecov-cli v11.2.8 run step
• Uses create-commit, create-report, and do-upload subcommands

Changes

-  codecov: codecov/codecov@<version>

-      - codecov/upload:
-          token: CODECOV_TOKEN
-          slug: trolley/dotnet-sdk
+      - run:
+          name: Upload coverage to Codecov
+          when: always
+          command: |
+            curl -Os https://github.com/codecov/codecov-cli/releases/download/v11.2.8/codecovcli_linux
+            chmod +x codecovcli_linux
+            ./codecovcli_linux create-commit -t $CODECOV_TOKEN --slug trolley/dotnet-sdk --git-service github -C $CIRCLE_SHA1
+            ./codecovcli_linux create-report -t $CODECOV_TOKEN --slug trolley/dotnet-sdk --git-service github -C $CIRCLE_SHA1
+            ./codecovcli_linux do-upload -t $CODECOV_TOKEN --slug trolley/dotnet-sdk --git-service github -C $CIRCLE_SHA1 --file coverage/coverage-final.json

Ticket

SRE-1580