Is your feature request related to a problem? Please describe.
Suggesting to create a new folder (i.e., monai/fl) containing the following subfolders and objects:

client:
ClientAlgo base class
MONAIAlgo reference implementation that can parse MONAI bundle configuration files
utils:
ExchangeObject, Filters and other helper/utility classes.

Describe the solution you'd like
Make MONAI FL-ready

Describe alternatives you've considered
n/a

Additional context
n/a