[minor] function to list AI Service instances

[boonware]

Issue

MASAIB-1321

Related

ibm-mas/cli#1763

Description

Add a new function to list AI Service instances in the cluster by checking for all AIServiceApp CRs.

[durera]

Can we eliminate the duplicate code, e.g.

def listAiServiceInstances(dynClient: DynamicClient) -> list:
  # This just calls listInstances()
def listMasInstances(dynClient: DynamicClient) -> list:
  # This just calls listInstances()
def listInstances(dynClient: DynamicClient, apiVersion: str, kind: str) -> list:
  # This has the implementation

[boonware]

Can we eliminate the duplicate code, e.g.

def listAiServiceInstances(dynClient: DynamicClient) -> list:
  # This just calls listInstances()
def listMasInstances(dynClient: DynamicClient) -> list:
  # This just calls listInstances()
def listInstances(dynClient: DynamicClient, apiVersion: str, kind: str) -> list:
  # This has the implementation

Code refactored as suggested.