Remove unused methods in ClientBean

[yux0]

Is your feature request related to a problem? Please describe.

1. Remove unused methods in ClientBean
2. Add new method GetAdminClient to align with Frontend Client

Describe the solution you'd like

1. Remove unused methods in ClientBean
2. Add new method GetAdminClient to align with Frontend Client

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[alexshtin]

I would remove entire ClientBean and replace it with proper fx injections.

[yiminc]

#5000

[dnr]

#5000 is for the persistence client bean only, not the rpc one that this issue is about