ARROW-11620: [Rust][DataFusion] Consistently use Arc<dyn TableProvider> rather than Box and Arc

[alamb]

NOTE: This is a backwards incompatible change in DataFusion

Inspired by a conversation with @seddonm1#9448 (comment) and #9445 as well as some upcoming needs in IOx (a consumer of DataFusion)

Rationale:

• No TableProvider APIs actually require ownership of the TableProvider (they all take &self)
• Internally DataFusion was storing the TableProvider as an Arc already and inconsistently uses Boxd and Arcd table providers (e.g. in LogicalPlan::TableScan)
• This change allows the same TableProvider instance to be reused easily for different ExecutionContexts

Changes

• Change all uses of TableProvider to be wrapped in Arc rather than Box

[github-actions]

https://issues.apache.org/jira/browse/ARROW-11620

[alamb]

This changes the signature of deregister_table to be consistent with other Rust ecosystem APIs and returned the previously registered item, if any

[alamb]

The Box passed into to register_table was already immediately wrapped in an Arc -- this PR allows the user of this API to keep a reference to the provider themselves.

[abreis]

Perhaps this could be a good time to also make this method return an Option<Arc<..>> so users can tell when they register a table over an existing table (consistent with deregister_table).

[alamb]

That is an excellent idea. I will make that change

[seddonm1]

👍 from me.

[jorgecarleitao]

LGTM. Nice cleanup!!

Note to reviewers: due to my screwup on master, the diff is large, but only the last two commits matter.

[alamb]

Thanks @jorgecarleitao -- I'll rebase this against master again just to keep the diff small

[alamb]

I plan to merge this tomorrow sometime unless anyone has any additionals comments or concerns