Simplify the KVM provider after the /simplify review

Collapse duplicated logic the review found in PR #5 without changing
behaviour: one releaseFinalizer helper for the four finalizer exits in
reconcileDelete, classify reusing isClassified and provider.Class, the
image URL check and format/firmware values shared from the provider
package, imageSource and the metadata parser embedding their config
structs instead of copying fields, and the SSH loader as a small struct
that keeps only the SSH fields and is seeded by New instead of loading
the key twice. Tracing builds its V(2)-only lists only at V(2).

Tests: drop a duplicate New test, fold near-identical tests into tables
(connection drops, metadata parsing, cached images), add mustSSHAuth,
and use wantClass where classes were checked by hand.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

internal/provider/kvm/trace.go

@@ -123,7 +123,10 @@ func (t *tracingAPI) DomainGetMetadata(d libvirt.Domain, typ int32, uri libvirt.
 func (t *tracingAPI) DomainInterfaceAddresses(d libvirt.Domain, source uint32, flags uint32) ([]libvirt.DomainInterface, error) {
 	c := t.begin("DomainInterfaceAddresses", "domain", d.Name, "source", libvirt.DomainInterfaceAddressesSource(source))
 	ifaces, err := t.inner.DomainInterfaceAddresses(d, source, flags)
-	c.detail("addresses", formatAddresses(ifaces)).done(err, "interfaces", len(ifaces))
+	if t.log.V(2).Enabled() {
+		c.detail("addresses", formatAddresses(ifaces))
+	}
+	c.done(err, "interfaces", len(ifaces))
 	return ifaces, err
 }
 
@@ -140,11 +143,14 @@ func formatAddresses(ifaces []libvirt.DomainInterface) []string {
 func (t *tracingAPI) ConnectListAllDomains(needResults int32, flags libvirt.ConnectListAllDomainsFlags) ([]libvirt.Domain, uint32, error) {
 	c := t.begin("ConnectListAllDomains", flagKV(int64(flags))...)
 	doms, n, err := t.inner.ConnectListAllDomains(needResults, flags)
-	names := make([]string, 0, len(doms))
-	for _, d := range doms {
-		names = append(names, d.Name)
+	if t.log.V(2).Enabled() {
+		names := make([]string, 0, len(doms))
+		for _, d := range doms {
+			names = append(names, d.Name)
+		}
+		c.detail("names", names)
 	}
-	c.detail("names", names).done(err, "count", len(doms))
+	c.done(err, "count", len(doms))
 	return doms, n, err
 }