Use transactions in commit API

[wjones127]

Right now, to commit a new version of a dataset the client must construct a Manifest correctly. This is a bit dangerous as serious issues could be caused by not constructing this correctly. In addition, manifests aren't easy to use to do conflict resolution on transactions.

We should switch to an API around transactions, that allow committing a transaction to a dataset, rather than a completely constructed state.

There could be a struct:

pub struct Transaction {
    updated_metadata: DatasetMetadata,
    new_fragments: Vec<Fragment>,
    updated_fragments: Vec<Fragment>,
    deleted_fragment_ids: Vec<u32>,
}

Then to commit a transaction, you could call either:

impl Dataset {
    /// Commit a transaction to an existing table
    pub async fn commit(
        &mut self,
        transaction: Transaction,
        retry_config: RetryConfig,
    ) -> Result<()> { ... }

    /// Commit a new table
    pub async fn commit_new(transaction: Transaction) -> Result<Self> { ... }
}

These methods could perform validation to make sure the transaction is correct, and can construct a valid manifest based on the state of the table. If a concurrent transaction beats the commit, then it could attempt to rebuild the manifest to create the next transaction, if that is allowed by conflict resolution algorithms.

[wjones127]

We added transaction concept in #1127, but we need to add them to the commit API.

[wjones127]

Note: someone started this in #982, so we should let them know when we implement this.

[wjones127]

Completed in #1194.