TestTransaction should implement Transaction instead of TransactionBase

Currently, `TestTransaction` implements TransactionBase, but still has a `commit()` and `close()` method with the same signature as the `Transaction` interface, which itself extends `AutoCloseable`. It should implement `Transaction` instead.

`TestTransaction` also has a `done()` method that does:

```java
try {
commit();
} finally {
close();
}
```

Once `TestTransaction` is `AutoCloseable`, inheriting that from `Transaction`, the calls to `done()` can, and should, be converted to calls to `commit()` at the end of a try-with-resources block, and the `done()` method should be removed. This will make the lifecycle management of test transactions in the test code more clear, rather than relying on the implied `close()` method inside the `done()`. It will also make the order of `commit()` calls more clear when writing/maintaining test code. With `commit()` hidden inside the `done()` method, it's not immediately obvious when they are called.

This proposal would cause code written like:

```java
TestTransaction tx = new TextTransaction();
// ... stuff here
tx.done(); // implied commit() and close()
```
to be written more explicitly as:

```java
try (TestTransaction tx = new TextTransaction()) {
// ... stuff here
tx.commit(); // explicit commit()
} // auto closed
```

This example doesn't look that much better, but it's a big improvement when there are multiple transactions being created, committed, and closed in a test.

Start by locating the Java TestTransaction class and all callers of its done() method. Review how those callers create and finish transactions, then convert them to try-with-resources with explicit commit() calls and verify that done() is no longer needed.

Written by the indexing model from the issue text.