hive-tls: the gateway leaf uses the services-issuer identity, not a hive's

swarm-services-cert issues the swarm-services leaf a self-signed gateway
serves, and on a host fronting no swarm name fetches the store's pki root.
It is gated on the gateway, not on a hive, yet its leaf pair was named
under deploy.hive-controller.tls and defaulted from the hive reader's cert
directory, and the root fetch presented the hive's own identity. A gateway
host with no hive had no such identity, so that branch was red by
construction.

- The pair moves to deploy.bao.servicesIssuerClient{Cert,Key}File, beside
  the store's other host-unit readers, and glue-bao-tls.nix defaults it on
  the store's host from the leaf it already mints. The old
  deploy.hive-controller.tls.baoClient{Cert,Key}File paths are
  mkRenamedOptionModule aliases. glue-services-issuer-bao-identity.nix,
  which derived the default from deploy.bao.clientCertFile, is gone.
- The no-swarm-name root fetch presents the services-issuer pair. The hive
  identity is now only hive-tls-resign's.
- A self-signed gateway with no pair fails evaluation, naming both options.
  A pair named but unreadable still fails the unit, naming the paths.

Refs #4921

nix/host-modules/default.nix

@@ -40,7 +40,6 @@
     ./glue-nats-oidc-client.nix
     ./glue-queue-agent-credential.nix
     ./glue-secret-publisher-bao-identity.nix
-    ./glue-services-issuer-bao-identity.nix
     ./glue-swarm-bao-otel-oidc-client.nix
     ./glue-swarm-otel-oidc-client.nix
     ./swarm-authelia-service.nix