Move keypair client to lib interfaces

For microversion testing framework, keypair client was
kept in tempest and modified for 2.2 and 2.10 microversion tests.

Now microversion stuff is all merged and we can move modified
keypair clients along with its schema files to lib folder.

Note- There is no backward compatibility changes in this interface.

Change-Id: Id8012ae123997142f645bcca8f250659fe73bb8e
diff --git a/tempest/clients.py b/tempest/clients.py
index fc0cc89..2a084d5 100644
--- a/tempest/clients.py
+++ b/tempest/clients.py
@@ -46,6 +46,7 @@
 from tempest.lib.services.compute.instance_usage_audit_log_client import \
     InstanceUsagesAuditLogClient
 from tempest.lib.services.compute.interfaces_client import InterfacesClient
+from tempest.lib.services.compute.keypairs_client import KeyPairsClient
 from tempest.lib.services.compute.limits_client import LimitsClient
 from tempest.lib.services.compute.migrations_client import MigrationsClient
 from tempest.lib.services.compute.networks_client import NetworksClient \
@@ -96,7 +97,6 @@
 from tempest import manager
 from tempest.services.baremetal.v1.json.baremetal_client import \
     BaremetalClient
-from tempest.services.compute.json.keypairs_client import KeyPairsClient
 from tempest.services.data_processing.v1_1.data_processing_client import \
     DataProcessingClient
 from tempest.services.database.json.flavors_client import \