Add file descriptor details to cat/nodes

cat/nodes currently does not report any details related to file descriptors. This adds the current number in use, the maximum number available as well as their ratio (percentage) to cat/nodes as hidden-by-default metrics. In addition, this also adds current heap usage (as a non-percentage of ts max) and ram usage (as a non-percerntage of its max) to allow tools to provide more granularity.

Closes #7652
testDanglingIndicesConflictWithAlias - wait for node left to be processed

O.w. delete index command may time out waiting for the node that left to confirm deletion
Tweaking upgrade test to improve reliability.
Docs: cross_type query needs to be cross_fields

Closes #8021
Fixing test to allow decimal numbers for load.