[Improvement] make Java GVFS configuration simple

[mchades]

What would you like to be improved?

The two Configuration item in Java GVFS seem to have fixed values, I think we can make them optional:

gravitino/docs/how-to-use-gvfs.md

Lines 49 to 52 in 6ad3d3b

	| Configuration item | Description | Default value | Required | Since version |
	|-------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|-------------------------------------|-----------------|
	| `fs.AbstractFileSystem.gvfs.impl` | The Gravitino Virtual File System abstract class, set it to `org.apache.gravitino.filesystem.hadoop.Gvfs`. | (none) | Yes | 0.5.0 |
	| `fs.gvfs.impl` | The Gravitino Virtual File System implementation class, set it to `org.apache.gravitino.filesystem.hadoop.GravitinoVirtualFileSystem`. | (none) | Yes | 0.5.0 |

How should we improve?

make them optional and give them default values

[mchades]

@yuqi1129 could you plz help to confirm?

[yuqi1129]

@yuqi1129 could you plz help to confirm?

Theoretically, we can utilize the service loader mechanism to optimize it. any paths that starts with gvfs will automatically use GravitinoVirtualFileSystem as the default implementation.