cmd: support type!=status in get --status-selector

`flux get --status-selector` only supported equality (`type=status`),
so finding objects that are not in a given state required multiple
invocations, e.g. listing everything that is not ready needed both
`Ready=False` and `Ready=Unknown`.

Add support for a negated selector `type!=status`. Since all resource
adapters delegate matching to the shared `statusMatches` helper and
filtering is centralised in `getRowsToPrint`, negation is implemented
purely in the parse/filter layer by inverting the match result. This
covers every resource type and the `--watch` path without touching the
per-resource adapters.

A missing condition is treated as not-matching by `statusMatches` (Flux
considers it "waiting to be reconciled"), so `Ready!=True` also surfaces
objects that have no Ready condition yet, i.e. the complete not-ready set:

    flux get all -A --status-selector Ready!=True

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: 3uzbcqje <3uzbcqje@addy.to>

cmd/flux/testdata/get/get_status_ready_true.golden

@@ -0,0 +1,2 @@
+NAME    	REVISION          	SUSPENDED	READY	MESSAGE                              
+gr-ready	main@sha1:696f056d	False    	True 	Fetched revision: main@sha1:696f056d