Preserve prereleased events when creating GitHub prereleases (#54724)

## Why

Publishing a draft prerelease emits a `published` event instead of a `prereleased` event.

## What changed

Create GitHub prereleases with `--draft=false` so they emit `prereleased` events. Keep stable releases as drafts until all asset uploads succeed.

GitOrigin-RevId: 145fd84f852d7ee9cb3c4edff7007a34c3389e1c

.github/workflows/rust-release.yml

@@ -1775,10 +1775,13 @@ jobs:
             --prerelease="$PRERELEASE"
           )
           if [[ "$exists" == false ]]; then
-            # Keep stable releases and prereleases private until all uploads succeed.
-            # Publishing a draft emits published rather than prereleased events.
+            # Prereleases must be created directly to keep prereleased events.
+            draft=true
+            if [[ "$PRERELEASE" == true ]]; then
+              draft=false
+            fi
             gh release create "$GITHUB_REF_NAME" "${release_args[@]}" \
-              --draft=true --verify-tag --latest=false
+              --draft="$draft" --verify-tag --latest=false
           fi
 
           mapfile -d '' assets < <(find dist -type f -print0 | sort -z)