fix(telemetry): Catch a non-std exception from the metrics pipeline setup

The startup path caught std::exception only. initMetrics() reaches the OTel SDK,
which can throw something outside that hierarchy, and escaping a member
initializer would stop the node starting.

The section states the rule it must not break: a telemetry failure never stops
the node, the global provider stays a no-op and every instrument call remains
valid. The new clause drops the half-built provider and logs, exactly as the
std::exception clause does.

~ApplicationImp() already carries the same pairing for the same reason.

src/libxrpl/telemetry/Telemetry.cpp

@@ -477,6 +477,16 @@ public:
                                       "continuing without metrics: "
                                    << e.what();
         }
+        catch (...)
+        {
+            // initMetrics() reaches third-party SDK code, which may throw
+            // something outside std::exception. Escaping a constructor on the
+            // startup path would stop the node starting, so drop the
+            // half-built provider exactly as the clause above does.
+            meterProvider_.reset();
+            JLOG(journal_.error()) << "Telemetry metrics pipeline failed to initialise, "
+                                      "continuing without metrics: unknown exception";
+        }
     }
 
     /**