Rails 6: Support lazy transactions

[aidanharan]

Lazy transactions changes required by rails/rails#32647

Before
https://travis-ci.org/github/rails-sqlserver/activerecord-sqlserver-adapter/jobs/680126303

6730 runs, 18723 assertions, 24 failures, 1 errors, 26 skips

After
https://travis-ci.org/github/rails-sqlserver/activerecord-sqlserver-adapter/jobs/680176451

6730 runs, 18725 assertions, 8 failures, 1 errors, 26 skips

[YehudaGold]

Hi, i implemented the lazy transactions support in my fork YehudaGold/activerecord-sqlserver-adapter (commit: YehudaGold@6b31617).
by adding the materialize_transactions guard rails/rails#32647 (comment).

I tried to open pull request to your fork:branch from my own but github don`t let my.
is this a permissions issue? can you merge the changes or implement them?

[aidanharan]

@ YehudaGold Merged your changes into my branch. Not sure why you couldnt create a PR (might be config of my fork). Thanks for your help.

[YehudaGold]

I found the problem in BasicsTest#test_0023_an empty transaction does not raise if preventing writes, because tests automatically wrapped in transaction the transaction in the test become SavepointTransaction and sql-server dont have release_savepoint` query so the assert should be corrected to 1.