Add ifnull method to db abstraction layer

[oc666]

Adding ifnull method to db abstraction.

Description

After PR 7428 regression raised on ms sql server driver, as ifnull does not supported on this DB.

To reproduce the issue just connect to SuiteCRM with ms sql server db.

Motivation and Context

mysql ifnull used in audit and it does not support in sql server.

How To Test This

Just configure your DB, and go change log of one of the entities with existing history.

Types of changes

• [X] Bug fix (non-breaking change which fixes an issue)
• [X] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Final checklist

• [X] My code follows the code style of this project found here.
• [ ] My change requires a change to the documentation.
• [X] I have read the How to Contribute guidelines.

[SuiteBot]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
12 out of 14 committers have signed the CLA.

:white_check_mark: pgorod
:white_check_mark: mattlorimer
:white_check_mark: QuickCRM
:white_check_mark: tsitle
:white_check_mark: JackBuchanan
:white_check_mark: Dillon-Brown
:white_check_mark: serfreeman1337
:white_check_mark: cameronblaikie
:white_check_mark: lazka
:white_check_mark: Jason-Dang
:white_check_mark: oc666
:white_check_mark: tsmgeek
:x: processflowca
:x: gitbnw
_{You have signed the CLA already but the status is still pending? Let us recheck it.}