descs: refactor GetAll* methods

This commit refactors the descs.Collection's GetAll* methods, which
return descriptors and other catalog metadata in bulk, to share a common
access path in which the descriptor's layers are properly aggregated.
This is non-trivial as there are numerous edge cases:
  - virtual schemas and objects exist for all databases and their
    descriptors don't reference the parent database at all,
  - descriptorless public schemas and temporary schemas only exist as
    namespace entries,
  - functions don't have namespace entries,
  - and so forth.

These new methods are delegated to by the existing methods which are now
deprecated.

Informs #64089.

Release note: None

pkg/bench/rttanalysis/testdata/benchmark_expectations

@@ -33,29 +33,29 @@ exp,benchmark
 14,CreateRole/create_role_with_no_options
 10,DropDatabase/drop_database_0_tables
 11,DropDatabase/drop_database_1_table
-12,DropDatabase/drop_database_2_tables
-13,DropDatabase/drop_database_3_tables
+11,DropDatabase/drop_database_2_tables
+11,DropDatabase/drop_database_3_tables
 18,DropRole/drop_1_role
 26,DropRole/drop_2_roles
 34,DropRole/drop_3_roles
 11,DropSequence/drop_1_sequence
 12,DropSequence/drop_2_sequences
-13,DropSequence/drop_3_sequences
+12,DropSequence/drop_3_sequences
 11,DropTable/drop_1_table
 12,DropTable/drop_2_tables
-13,DropTable/drop_3_tables
+12,DropTable/drop_3_tables
 12,DropView/drop_1_view
 13,DropView/drop_2_views
 13,DropView/drop_3_views
 10,Grant/grant_all_on_1_table
-11,Grant/grant_all_on_2_tables
-11,Grant/grant_all_on_3_tables
+10,Grant/grant_all_on_2_tables
+10,Grant/grant_all_on_3_tables
 11,GrantRole/grant_1_role
 15,GrantRole/grant_2_roles
-3,ORMQueries/activerecord_type_introspection_query
-6,ORMQueries/django_table_introspection_1_table
-6,ORMQueries/django_table_introspection_4_tables
-6,ORMQueries/django_table_introspection_8_tables
+4,ORMQueries/activerecord_type_introspection_query
+8,ORMQueries/django_table_introspection_1_table
+8,ORMQueries/django_table_introspection_4_tables
+8,ORMQueries/django_table_introspection_8_tables
 2,ORMQueries/has_column_privilege_using_attnum
 2,ORMQueries/has_column_privilege_using_column_name
 1,ORMQueries/has_schema_privilege_1
@@ -69,19 +69,19 @@ exp,benchmark
 6,ORMQueries/has_table_privilege_5
 85,ORMQueries/hasura_column_descriptions
 85,ORMQueries/hasura_column_descriptions_8_tables
-6,ORMQueries/hasura_column_descriptions_modified
-4,ORMQueries/information_schema._pg_index_position
-3,ORMQueries/pg_attribute
-3,ORMQueries/pg_class
-7,ORMQueries/pg_is_other_temp_schema
-7,ORMQueries/pg_is_other_temp_schema_multiple_times
-4,ORMQueries/pg_my_temp_schema
-4,ORMQueries/pg_my_temp_schema_multiple_times
-4,ORMQueries/pg_namespace
-3,ORMQueries/pg_type
+8,ORMQueries/hasura_column_descriptions_modified
+6,ORMQueries/information_schema._pg_index_position
+5,ORMQueries/pg_attribute
+5,ORMQueries/pg_class
+9,ORMQueries/pg_is_other_temp_schema
+9,ORMQueries/pg_is_other_temp_schema_multiple_times
+6,ORMQueries/pg_my_temp_schema
+6,ORMQueries/pg_my_temp_schema_multiple_times
+6,ORMQueries/pg_namespace
+5,ORMQueries/pg_type
 10,Revoke/revoke_all_on_1_table
-11,Revoke/revoke_all_on_2_tables
-11,Revoke/revoke_all_on_3_tables
+10,Revoke/revoke_all_on_2_tables
+10,Revoke/revoke_all_on_3_tables
 9,RevokeRole/revoke_1_role
 11,RevokeRole/revoke_2_roles
 1,SystemDatabaseQueries/select_system.users_with_empty_database_Name