PG-1437 Add a test for changing the keyring provider type

Longterm we may want to allow this to prevent users from breaking stuff
but for now we add a test to make it clear that changing the provider is
currently allowed.

Author: jeltz

contrib/pg_tde/expected/key_provider.out

@@ -101,7 +101,20 @@ SELECT id, provider_name FROM pg_tde_list_all_global_key_providers();
  -2 | file-keyring2
 (2 rows)
 
--- TODO: verify that we can also can change the type of it
+\getenv root_token ROOT_TOKEN
+SELECT pg_tde_change_database_key_provider_vault_v2('file-provider', :'root_token', 'http://127.0.0.1:8200', 'secret', NULL);
+ pg_tde_change_database_key_provider_vault_v2 
+----------------------------------------------
+                                            1
+(1 row)
+
+SELECT id, provider_name, provider_type FROM pg_tde_list_all_database_key_providers();
+ id | provider_name  | provider_type 
+----+----------------+---------------
+  1 | file-provider  | vault-v2
+  2 | file-provider2 | file
+(2 rows)
+
 -- fails
 SELECT pg_tde_delete_database_key_provider('file-provider');
 ERROR:  Can't delete a provider which is currently in use

contrib/pg_tde/expected/key_provider_1.out

@@ -102,7 +102,20 @@ SELECT id, provider_name FROM pg_tde_list_all_global_key_providers();
  -3 | file-keyring2
 (3 rows)
 
--- TODO: verify that we can also can change the type of it
+\getenv root_token ROOT_TOKEN
+SELECT pg_tde_change_database_key_provider_vault_v2('file-provider', :'root_token', 'http://127.0.0.1:8200', 'secret', NULL);
+ pg_tde_change_database_key_provider_vault_v2 
+----------------------------------------------
+                                            1
+(1 row)
+
+SELECT id, provider_name, provider_type FROM pg_tde_list_all_database_key_providers();
+ id | provider_name  | provider_type 
+----+----------------+---------------
+  1 | file-provider  | vault-v2
+  2 | file-provider2 | file
+(2 rows)
+
 -- fails
 SELECT pg_tde_delete_database_key_provider('file-provider');
 ERROR:  Can't delete a provider which is currently in use

contrib/pg_tde/sql/key_provider.sql

@@ -32,7 +32,9 @@ SELECT pg_tde_add_global_key_provider_file('file-keyring2','/tmp/pg_tde_test_key
 
 SELECT id, provider_name FROM pg_tde_list_all_global_key_providers();
 
--- TODO: verify that we can also can change the type of it
+\getenv root_token ROOT_TOKEN
+SELECT pg_tde_change_database_key_provider_vault_v2('file-provider', :'root_token', 'http://127.0.0.1:8200', 'secret', NULL);
+SELECT id, provider_name, provider_type FROM pg_tde_list_all_database_key_providers();
 
 -- fails
 SELECT pg_tde_delete_database_key_provider('file-provider');