Merge branch 'main' into fix/upgrade-report-matrix

The upgrade report only ever showed the requested deb URLs and a case
table. The nightly chain runs died installing the OLD package (default
from_version 1.0.0-rc.4-preview.1 has no .deb asset on its release, and
release 1.0.0-rc.4 ships none either), leaving an empty Total: 0 report
with no indication of what was upgraded.

- Default from_version is now 1.0.0-rc.3 (ships rustfs_1.0.0.rc.3_amd64.deb).
  Matches the auto-testing default from PR #32.
- The report generator also parses the [UPG-TOPO] lines the suite now
  emits and renders an 'Upgrade Matrix' section: per topology and KMS
  backend, the versions actually in place before/after (captured via
  'rustfs --version' on the node) and the aggregated result. When the
  suite dies before any topology completes, the matrix says so instead
  of silently showing nothing.

crates/ecstore/src/bucket/sealed_credentials.rs

@@ -203,8 +203,9 @@ mod tests {
     use parking_lot::Mutex;
     use std::collections::BTreeMap;
 
-    fn encode_context(context: &BTreeMap<String, String>) -> String {
-        serde_json::to_string(context).expect("context serializes")
+    fn encode_context(context: &HashMap<String, String>) -> String {
+        let ordered = context.iter().collect::<BTreeMap<_, _>>();
+        serde_json::to_string(&ordered).expect("context serializes")
     }
 
     /// Stands in for the KMS-backed sealer: records the context it was called