[ES|QL] Prevent fused fields from being pushed into StubRelations #138620
Description
Uncovered as a result of running queries like
FROM k8s-downsampled
| INLINE STATS tx_max = MAX(network.eth0.tx) BY pod
| SORT @timestamp, cluster, pod
| KEEP @timestamp, cluster, pod, network.eth0.tx, tx_max
| LIMIT 9
;
During the rule logical.PropagateInlineEvals, we end up with a Logical Plan change like the following:
\_StubRelation[[@timestamp{f}#15, cluster{f}#14, network.eth0.tx{f}#19, pod{f}#16]] !
\_StubRelation[[@timestamp{f}#15, cluster{f}#14, network.eth0.tx{f}#19, pod{f}#16, $$MAX(network.eth>$MAX$0{r$}#20]]