feat(policy): add built-in KMS role policies and a negative authorization matrix (#5588)

* feat(policy): add built-in KMS role policies

KMSKeyAdministrator, KMSKeyUser and KMSAuditor ship as canned identity
policies so operators can express KMS role separation without hand-writing
the resource grammar. They grant only kms actions, so they compose with an
existing data-plane policy, and none of them confers kms:Configure,
kms:ServiceControl, kms:ClearCache, kms:Backup or kms:Restore.

* docs(kms): document per-key KMS authorization and the role templates

* test(kms): add an end-to-end negative authorization matrix

Covers the admin and SSE-KMS planes for a wrong identity, a wrong key, a
wrong action and an explicit Deny, each preceded by a positive control so a
denial cannot be an unpropagated policy. SSE-S3 and unencrypted objects are
asserted to stay exempt.

* test(replication): pin the SSE-KMS contract with per-key authorization on

The replication worker carries no request identity, so it must stay exempt
from SSE-KMS key authorization. Running the existing contract with the
switch enabled makes a regression in that exemption visible here.

crates/e2e_test/src/replication_extension_test.rs

@@ -1507,6 +1507,10 @@ async fn build_sse_replication_pair(
             ("RUSTFS_KMS_KEY_DIR", source_kms_key_dir.as_str()),
             ("RUSTFS_KMS_DEFAULT_KEY_ID", REPL17_KMS_KEY_ID),
             ("RUSTFS_KMS_ALLOW_INSECURE_DEV_DEFAULTS", "true"),
+            // Per-key KMS authorization is on so this contract is pinned in the
+            // configuration replication will eventually ship with: the replication
+            // worker carries no request identity and must stay exempt.
+            ("RUSTFS_KMS_ENFORCE_SSE_KEY_POLICY", "true"),
         ]);
     }
     source_env.start_rustfs_server_with_env(vec![], &source_process_env).await?;
@@ -1519,6 +1523,7 @@ async fn build_sse_replication_pair(
             ("RUSTFS_KMS_KEY_DIR", target_kms_key_dir.as_str()),
             ("RUSTFS_KMS_DEFAULT_KEY_ID", REPL17_KMS_KEY_ID),
             ("RUSTFS_KMS_ALLOW_INSECURE_DEV_DEFAULTS", "true"),
+            ("RUSTFS_KMS_ENFORCE_SSE_KEY_POLICY", "true"),
         ]);
     }
     target_env