Most of the time, generated SQL is intended to run within a transacton.

We normally don't need to worry about it. However, there are situations

in which some generated SQL must run in either a brand-new transaction,

or completely outside of a transaction.
The recent introduction of SQLExecutor was built to lay the ground

work for this. This change follows up by introducing new wrappers for

lists of SQL statements: NewTransactionSQL, and NoTransactionSQL.

Any list of statements in generated SQL can be wrapped in one of these

to, respectively, execute in a brand-new transaction (committing any

previous one first) or execute outside of a transaction.
The SQLite code for renaming a primary key has been updated to make use

of this. This code needed to commit a transaction, execute new code in

another transaction, and then send s VACUUM comamnd outside of a

transaction. The method used for this was hacky and falls apart with

some in-progress work. Now, using these wrappers, it's safe,

future-proof, and compatible with other transaction work.

Unit tests passed on all versions of Python and Django.
Tested creating and updating databases.