DMS v2.1 cluster management & specification implementation

[sgmv]

What this PR does / why we need it

Covers additional instance management for DMS.

Instance Management

Specification Modification Management

Special notes for your reviewer

Test passed.

=== RUN TestDmsManagement
instances_test.go:76: Attempting to create DMSv2.1 instance
instances_test.go:120: DMSv2.1 instance successfully created: 3c5c891f-78ce-4436-82f4-99a96e34d4bb
instances_management_test.go:36: DMSv2.1 password updated
instances_management_test.go:43: DMSv2.1 auto topic creation enabled
instances_management_test.go:47: DMSv2.1 consumer group created
instances_management_test.go:55: got consumergroup response:
instances_management_test.go:57: DMSv2.1 consumer group get function done
instances_management_test.go:59: got detailed consumergroup response:
instances_management_test.go:61: DMSv2.1 consumer group detailed get function done
instances_management_test.go:65: DMSv2.1 list of consumer group is done
instances_management_test.go:69: DMSv2.1 get coordinator is done
instances_management_test.go:73: DMSv2.1 get disk usage is done
instances_management_test.go:77: DMSv2.1 get metadata is done
instances_management_test.go:81: DMSv2.1 get specification is done
instances_management_test.go:52: DMSv2.1 consumer group deleted
instances_test.go:126: Attempting to delete DMSv2.1 instance: 3c5c891f-78ce-4436-82f4-99a96e34d4bb
instances_test.go:133: DMSv2.1 instance deleted successfully: 3c5c891f-78ce-4436-82f4-99a96e34d4bb
--- PASS: TestDmsManagement (666.06s)
PASS