[Improvement] GVFS need to reuse UsergroupInformation credential

### What would you like to be improved?

Now, GVFS needs the configuration
```
/** The authentication type for simple authentication. */
public static final String SIMPLE_AUTH_TYPE = "simple";

/** The authentication type for oauth2 authentication. */
public static final String OAUTH2_AUTH_TYPE = "oauth2";

/** The authentication type for kerberos authentication. */
public static final String KERBEROS_AUTH_TYPE = "kerberos";

// oauth2
/** The configuration key prefix for oauth2 */
public static final String FS_GRAVITINO_CLIENT_OAUTH2_PREFIX = "fs.gravitino.client.oauth2.";

/** The configuration key for the URI of the default OAuth server. */
public static final String FS_GRAVITINO_CLIENT_OAUTH2_SERVER_URI_KEY =
"fs.gravitino.client.oauth2.serverUri";

/** The configuration key for the client credential. */
public static final String FS_GRAVITINO_CLIENT_OAUTH2_CREDENTIAL_KEY =
"fs.gravitino.client.oauth2.credential";

/** The configuration key for the path which to get the token. */
public static final String FS_GRAVITINO_CLIENT_OAUTH2_PATH_KEY =
"fs.gravitino.client.oauth2.path";

/** The configuration key for the scope of the token. */
public static final String FS_GRAVITINO_CLIENT_OAUTH2_SCOPE_KEY =
"fs.gravitino.client.oauth2.scope";

/** The configuration key prefix for kerberos */
public static final String FS_GRAVITINO_CLIENT_KERBEROS_PREFIX = "fs.gravitino.client.kerberos.";

/** The configuration key for the principal. */
public static final String FS_GRAVITINO_CLIENT_KERBEROS_PRINCIPAL_KEY =
"fs.gravitino.client.kerberos.principal";

/** The configuration key for the keytab file path corresponding to the principal. */
public static final String FS_GRAVITINO_CLIENT_KERBEROS_KEYTAB_FILE_PATH_KEY =
"fs.gravitino.client.kerberos.keytabFilePath";

/** The configuration key for the maximum capacity of the Gravitino fileset cache. */
public static final String FS_GRAVITINO_FILESET_CACHE_MAX_CAPACITY_KEY =
"fs.gravitino.fileset.cache.maxCapacity";
```
Actually, we should reuse the UserGroupInformation, especially for simple mode and Kerberos mode.
For simple mode. we should keep consistent with `UserGroupInformation.getCurrentUser`
For Keberos mode, we should keep consistent with `UserGroupInformation.getCredentials`.

### How should we improve?

ctually, we should reuse the UserGroupInformation, especially for simple mode and Kerberos mode.
For simple mode. we should keep consistent with `UserGroupInformation.getCurrentUser`
For Keberos mode, we should keep consistent with `UserGroupInformation.getCredentials`.

Start by locating the GVFS authentication and configuration code, then trace how simple and Kerberos modes currently obtain credentials. Compare those paths with UserGroupInformation.getCurrentUser and UserGroupInformation.getCredentials; done means both modes consistently reuse the UserGroupInformation state without requiring duplicate configuration.

Written by the indexing model from the issue text.