[release-1.14] Improve istioctl options command description

[istio-testing]

Manual cherrypick required.

#38236 failed to apply on top of branch "release-1.14":

Applying: improve description
Applying: revise and add releasenotes
Applying: revise run to runE
Applying: lint
Using index info to reconstruct a base tree...
M	istioctl/cmd/root.go
Falling back to patching base and 3-way merge...
Auto-merging istioctl/cmd/root.go
CONFLICT (content): Merge conflict in istioctl/cmd/root.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0004 lint
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

[howardjohn]

#40967