[FEATURE] Make fileset python client pluggable

### Describe the feature

As Gravitino has support fileset that can be easily pluggable, for example, users or developers can custom fileset type and access this fileset through GVFS Java client without changing Gravitino code. However, the Python client needs to be changed to access this fileset.

We need to make the Python client capable of accessing custom fileset without modifying the code and introduce a mechanism similar to HCFS.

### Motivation

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### Describe the solution

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### Additional context

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Start by locating the Python client’s fileset access path and compare it with the existing HCFS mechanism. Define how custom fileset types can be registered and accessed without modifying Gravitino code; done means a custom fileset works through the Python client.

Written by the indexing model from the issue text.