Add ActiveRecord::Base.connection.with_advisory_lock

[rafaelfranca]

This method allow applications to obtain an exclusive session level advisory lock, if available, for the duration of the block.

If another session already have the lock, the method will return false and the block will not be executed.

[eileencodes]

I stumbled across this while searching for another advisory lock PR. For historical purposes, I'm linking the revert commit here 561fa1e

This reverts commit 1ab4dbf8aad83a451c3d2a6c24bc87012b2303c2.

After speaking with Shopify's resident database experts, they
recommended me to not expose this feature in the public API.
The reason why they don't recommend it, is that this kind of locking
break multiplexing mechanisms like ProxySQL and can decrease the
resiliency of the application.

My original motivation was to remove a monkey patch in our application
and since we are not planning to allow people to use that feature in our
application anymore there is no reason to me expose this locking mechanism
anymore in the framework.