Fix GHA upload-test-results (#6091)

## What changed?
<!-- Describe what has changed in this PR -->

Separate test execution and test result upload. And check XML file
exists.

Previously introduced here
https://github.com/temporalio/temporal/pull/6049

## Why?
<!-- Tell your future self why have you made these changes -->

make aborts execution when the previous target fails. Oops.

## How did you test it?
<!-- How have you verified this change? Tested locally? Added a unit
test? Checked in staging env? -->

Scenarios:

- [x] no Buildkite secret set
- [x] make target has test errors
- [x] make target has no test errors
- [x] make target aborts (no XML file written)

## Potential risks
<!-- Assuming the worst case, what can be broken when deploying this
change to production? -->

## Documentation
<!-- Have you made sure this change doesn't falsify anything currently
stated in `docs/`? If significant
new behavior is added, have you described that in `docs/`? -->

## Is hotfix candidate?
<!-- Is this PR a hotfix candidate or does it require a notification to
be sent to the broader community? (Yes/No) -->

develop/upload-test-results.sh

@@ -8,17 +8,18 @@ fi
 echo "uploading test results from $(pwd)"
 
 for file in *.junit.xml; do
-    echo "uploading ${file}"
+  [ -e "$file" ] || continue
+  echo "uploading ${file}"
 
-    curl -i -X POST \
-      -H "Authorization: Token token=${BUILDKITE_ANALYTICS_TOKEN}" \
-      -F "data=@${file}" \
-      -F "format=junit" \
-      -F "run_env[CI]=github_actions" \
-      -F "run_env[key]=${GITHUB_ACTION}-${GITHUB_RUN_NUMBER}-${GITHUB_RUN_ATTEMPT}" \
-      -F "run_env[number]=${GITHUB_RUN_NUMBER}" \
-      -F "run_env[branch]=${GITHUB_REF}" \
-      -F "run_env[commit_sha]=${GITHUB_SHA}" \
-      -F "run_env[url]=https://github.com/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID}" \
-      https://analytics-api.buildkite.com/v1/uploads
+  curl -i -X POST \
+    -H "Authorization: Token token=${BUILDKITE_ANALYTICS_TOKEN}" \
+    -F "data=@${file}" \
+    -F "format=junit" \
+    -F "run_env[CI]=github_actions" \
+    -F "run_env[key]=${GITHUB_ACTION}-${GITHUB_RUN_NUMBER}-${GITHUB_RUN_ATTEMPT}" \
+    -F "run_env[number]=${GITHUB_RUN_NUMBER}" \
+    -F "run_env[branch]=${GITHUB_REF}" \
+    -F "run_env[commit_sha]=${GITHUB_SHA}" \
+    -F "run_env[url]=https://github.com/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID}" \
+    https://analytics-api.buildkite.com/v1/uploads
 done