Add privacy as CODEOWNER for confidentialrelay paths in core (#22762)

* Add privacy as CODEOWNER for core/capabilities/confidentialrelay

confidentialrelay holds the relay-DON authorization logic (PRIV-433, PRIV-458),
which is privacy-owned security code. It currently inherits /core/capabilities/
(keystone + capabilities-team) with no privacy entry. Add privacy alongside the
existing owners so privacy can review and approve changes there, e.g. #22516
and #22703.

* Make confidentialrelay CODEOWNERS privacy-only (capabilities + gateway)

Both confidentialrelay paths are purely privacy's confidential-relay code:
the capability handler (core/capabilities/confidentialrelay) and the gateway
handler (core/services/gateway/handlers/confidentialrelay). Assign both to
@smartcontractkit/privacy outright, mirroring confidentialhttp in chainlink-common.

* Add system-tests confidentialrelay CODEOWNERS for privacy

Author: nadahalli

.github/CODEOWNERS

@@ -24,6 +24,7 @@
 /core/capabilities/ccip/ccipsolana/ @smartcontractkit/bix-build
 /core/capabilities/ccip/ccipnoop/ @smartcontractkit/bix-build
 /core/capabilities/ccip/ccipton/ @smartcontractkit/bix-build
+/core/capabilities/confidentialrelay/ @smartcontractkit/privacy
 
 # To be deprecated in Chainlink V3
 /core/services/job/ @smartcontractkit/foundations @smartcontractkit/core
@@ -63,6 +64,8 @@
 /core/services/registrysyncer/ @smartcontractkit/keystone
 /core/services/workflows/ @smartcontractkit/keystone
 /core/services/standardcapabilities/ @smartcontractkit/keystone
+/core/services/gateway/handlers/confidentialrelay/ @smartcontractkit/privacy
+/system-tests/lib/cre/features/confidentialrelay/ @smartcontractkit/privacy
 /core/scripts/keystone/ @smartcontractkit/keystone
 
 # GQL API