Expand support for SpatVector objects

[dieghernan]

As part of the improvements #1

Create SpatVector methods for:

• arrange()
• glimpe() (also for SpatRasters).
• distinct()
• *_join()
• group_*()
• summarise()
• count()/tally()
• bind_rows()/cols()

New coercing and helper functions:

• as_spatvector()
• as_sf()
• is_grouped_spatvector()

Review existing methods

• Remove dispatch to sf an add own internal way
• Revise and recheck to make them compatible with the new group_by.SpatVector() method.